diff --git a/ansible_mitogen/mixins.py b/ansible_mitogen/mixins.py
index 3953eb52..dadf2c17 100644
--- a/ansible_mitogen/mixins.py
+++ b/ansible_mitogen/mixins.py
@@ -103,13 +103,10 @@ class ActionModuleMixin(ansible.plugins.action.ActionBase):
 
         # required for python interpreter discovery
         connection.templar = self._templar
-        self._finding_python_interpreter = False
-        self._rediscovered_python = False
-        # redeclaring interpreter discovery vars here in case running ansible < 2.8.0
-        self._discovered_interpreter_key = None
-        self._discovered_interpreter = False
-        self._discovery_deprecation_warnings = []
-        self._discovery_warnings = []
+
+        self._mitogen_discovering_interpreter = False
+        self._mitogen_interpreter_candidate = None
+        self._mitogen_rediscovered_interpreter = False
 
     def run(self, tmp=None, task_vars=None):
         """
@@ -402,7 +399,7 @@ class ActionModuleMixin(ansible.plugins.action.ActionBase):
             # only cache discovered_interpreter if we're not running a rediscovery
             # rediscovery happens in places like docker connections that could have different
             # python interpreters than the main host
-            if not self._rediscovered_python:
+            if not self._mitogen_rediscovered_interpreter:
                 result['ansible_facts'][self._discovered_interpreter_key] = self._discovered_interpreter
 
         if self._discovery_warnings:
@@ -462,7 +459,7 @@ class ActionModuleMixin(ansible.plugins.action.ActionBase):
         # calling exec_command until we run into the right python we'll use
         # chicken-and-egg issue, mitogen needs a python to run low_level_execute_command
         # which is required by Ansible's discover_interpreter function
-        if self._finding_python_interpreter:
+        if self._mitogen_discovering_interpreter:
             possible_pythons = [
                 '/usr/bin/python',
                 'python3',
@@ -479,32 +476,27 @@ class ActionModuleMixin(ansible.plugins.action.ActionBase):
             # not used, just adding a filler value
             possible_pythons = ['python']
 
-        def _run_cmd():
-            return self._connection.exec_command(
-                cmd=cmd,
-                in_data=in_data,
-                sudoable=sudoable,
-                mitogen_chdir=chdir,
-            )
-
         for possible_python in possible_pythons:
             try:
-                self._possible_python_interpreter = possible_python
-                rc, stdout, stderr = _run_cmd()
+                self._mitogen_interpreter_candidate = possible_python
+                rc, stdout, stderr = self._connection.exec_command(
+                    cmd, in_data, sudoable, mitogen_chdir=chdir,
+                )
             # TODO: what exception is thrown?
             except:
                 # we've reached the last python attempted and failed
-                # TODO: could use enumerate(), need to check which version of python first had it though
-                if possible_python == 'python':
+                if possible_python == possible_pythons[-1]:
                     raise
                 else:
                     continue
 
         stdout_text = to_text(stdout, errors=encoding_errors)
+        stderr_text = to_text(stderr, errors=encoding_errors)
 
         return {
             'rc': rc,
             'stdout': stdout_text,
             'stdout_lines': stdout_text.splitlines(),
-            'stderr': stderr,
+            'stderr': stderr_text,
+            'stderr_lines': stderr_text.splitlines(),
         }
diff --git a/ansible_mitogen/planner.py b/ansible_mitogen/planner.py
index 6490afce..2915f4b7 100644
--- a/ansible_mitogen/planner.py
+++ b/ansible_mitogen/planner.py
@@ -615,6 +615,23 @@ def _fix_py35(invocation, module_source):
         invocation._overridden_sources[invocation.module_path] = module_source
 
 
+def _fix_dnf(invocation, module_source):
+    """
+    Handles edge case where dnf ansible module showed failure due to a missing import in the dnf module.
+    Specifically addresses errors like "Failed loading plugin 'debuginfo-install': module 'dnf' has no attribute 'cli'".
+    https://github.com/mitogen-hq/mitogen/issues/1143
+    This issue is resolved by adding 'dnf.cli' to the import statement in the module source.
+    This works in vanilla Ansible but not in Mitogen otherwise.
+    """
+    if invocation.module_name in {'ansible.builtin.dnf', 'ansible.legacy.dnf', 'dnf'} and \
+            invocation.module_path not in invocation._overridden_sources:
+        module_source = module_source.replace(
+            b"import dnf\n",
+            b"import dnf, dnf.cli\n"
+        )
+        invocation._overridden_sources[invocation.module_path] = module_source
+
+
 def _load_collections(invocation):
     """
     Special loader that ensures that `ansible_collections` exist as a module path for import
@@ -652,6 +669,7 @@ def invoke(invocation):
 
         module_source = invocation.get_module_source()
         _fix_py35(invocation, module_source)
+        _fix_dnf(invocation, module_source)
         _planner_by_path[invocation.module_path] = _get_planner(
             invocation,
             module_source
diff --git a/ansible_mitogen/target.py b/ansible_mitogen/target.py
index ee4cb398..33bcb107 100644
--- a/ansible_mitogen/target.py
+++ b/ansible_mitogen/target.py
@@ -647,11 +647,10 @@ def set_file_owner(path, owner, group=None, fd=None):
     else:
         gid = os.getegid()
 
-    if fd is not None and hasattr(os, 'fchown'):
-        os.fchown(fd, (uid, gid))
+    if fd is not None:
+        os.fchown(fd, uid, gid)
     else:
-        # Python<2.6
-        os.chown(path, (uid, gid))
+        os.chown(path, uid, gid)
 
 
 def write_path(path, s, owner=None, group=None, mode=None,
@@ -741,7 +740,7 @@ def set_file_mode(path, spec, fd=None):
         mode = os.stat(path).st_mode
         new_mode = apply_mode_spec(spec, mode)
 
-    if fd is not None and hasattr(os, 'fchmod'):
+    if fd is not None:
         os.fchmod(fd, new_mode)
     else:
         os.chmod(path, new_mode)
diff --git a/ansible_mitogen/transport_config.py b/ansible_mitogen/transport_config.py
index effb4d62..22afd197 100644
--- a/ansible_mitogen/transport_config.py
+++ b/ansible_mitogen/transport_config.py
@@ -87,8 +87,8 @@ def run_interpreter_discovery_if_necessary(s, task_vars, action, rediscover_pyth
     it could be different than what's ran on the host
     """
     # keep trying different interpreters until we don't error
-    if action._finding_python_interpreter:
-        return action._possible_python_interpreter
+    if action._mitogen_discovering_interpreter:
+        return action._mitogen_interpreter_candidate
 
     if s in ['auto', 'auto_legacy', 'auto_silent', 'auto_legacy_silent']:
         # python is the only supported interpreter_name as of Ansible 2.8.8
@@ -102,13 +102,13 @@ def run_interpreter_discovery_if_necessary(s, task_vars, action, rediscover_pyth
             # if we're rediscovering python then chances are we're running something like a docker connection
             # this will handle scenarios like running a playbook that does stuff + then dynamically creates a docker container,
             # then runs the rest of the playbook inside that container, and then rerunning the playbook again
-            action._rediscovered_python = True
+            action._mitogen_rediscovered_interpreter = True
 
             # blow away the discovered_interpreter_config cache and rediscover
             del task_vars['ansible_facts'][discovered_interpreter_config]
 
         if discovered_interpreter_config not in task_vars['ansible_facts']:
-            action._finding_python_interpreter = True
+            action._mitogen_discovering_interpreter = True
             # fake pipelining so discover_interpreter can be happy
             action._connection.has_pipelining = True
             s = ansible.executor.interpreter_discovery.discover_interpreter(
@@ -128,7 +128,7 @@ def run_interpreter_discovery_if_necessary(s, task_vars, action, rediscover_pyth
         action._discovered_interpreter_key = discovered_interpreter_config
         action._discovered_interpreter = s
 
-    action._finding_python_interpreter = False
+    action._mitogen_discovering_interpreter = False
     return s
 
 
diff --git a/docs/changelog.rst b/docs/changelog.rst
index 7cd795ab..ba40784f 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -18,6 +18,28 @@ To avail of fixes in an unreleased version, please download a ZIP file
 `directly from GitHub <https://github.com/mitogen-hq/mitogen/>`_.
 
 
+v0.3.22 (2025-02-04)
+--------------------
+
+* :gh:issue:`1213` tests: Enable default Python warnings
+* :gh:issue:`1111` :mod:`mitogen`: Replace uses of deprecated
+  :py:func:`pkgutil.find_loader`
+* :gh:issue:`1213` :mod:`mitogen`: Fix unclosed file in first stage
+* :gh:issue:`1213` tests: Fix unclosed file in fd_check script
+* :gh:issue:`1213` :mod:`ansible_mitogen`: Don't redeclare Ansible interpreter
+  discovery attributes
+* :gh:issue:`1213` :mod:`ansible_mitogen`: Rename Mitogen interpreter discovery
+  attributes
+* :gh:issue:`1213` :mod:`ansible_mitogen`: Decouple possible_pythons order &
+  error handling
+* :gh:issue:`1213` :mod:`ansible_mitogen`: Return ``stderr_lines`` from
+  ``_low_level_execute_command()``
+* :gh:issue:`1227` tests: Name transport_config tests that use ``mitogen_via``
+* :gh:issue:`1143` :mod:`ansible_mitogen`: Fix dnf module include for dnf.cli
+* :gh:issue:`1234` :mod:`ansible_mitogen`: Fix :exc:`TypeError` in
+  :func:`ansible_mitogen.target.set_file_owner`
+
+
 v0.3.21 (2025-01-20)
 --------------------
 
diff --git a/mitogen/__init__.py b/mitogen/__init__.py
index bbf807dc..61fce888 100644
--- a/mitogen/__init__.py
+++ b/mitogen/__init__.py
@@ -35,7 +35,7 @@ be expected. On the slave, it is built dynamically during startup.
 
 
 #: Library version as a tuple.
-__version__ = (0, 3, 21)
+__version__ = (0, 3, 22)
 
 
 #: This is :data:`False` in slave contexts. Previously it was used to prevent
diff --git a/mitogen/master.py b/mitogen/master.py
index 865c9dc1..927ccaf1 100644
--- a/mitogen/master.py
+++ b/mitogen/master.py
@@ -54,21 +54,33 @@ try:
     import importlib.machinery
     import importlib.util
     from _imp import is_builtin as _is_builtin
+
+    def _find_loader(fullname):
+        try:
+            maybe_spec = importlib.util.find_spec(fullname)
+        except (ImportError, AttributeError, TypeError, ValueError):
+            exc = sys.exc_info()[1]
+            raise ImportError(*exc.args)
+        try:
+            return maybe_spec.loader
+        except AttributeError:
+            return None
 except ImportError:
     # Python < 3.4, PEP 302 Import Hooks
     import imp
     from imp import is_builtin as _is_builtin
 
+    try:
+        from pkgutil import find_loader as _find_loader
+    except ImportError:
+        # Python < 2.5
+        from mitogen.compat.pkgutil import find_loader as _find_loader
+
 try:
     import sysconfig
 except ImportError:
     sysconfig = None
 
-if not hasattr(pkgutil, 'find_loader'):
-    # find_loader() was new in >=2.5, but the modern pkgutil.py syntax has
-    # been kept intentionally 2.3 compatible so we can reuse it.
-    from mitogen.compat import pkgutil
-
 import mitogen
 import mitogen.core
 import mitogen.minify
@@ -175,7 +187,7 @@ def get_child_modules(path, fullname):
         return [to_text(name) for _, name, _ in pkgutil.iter_modules([mod_path])]
     else:
         # we loaded some weird package in memory, so we'll see if it has a custom loader we can use
-        loader = pkgutil.find_loader(fullname)
+        loader = _find_loader(fullname)
         return [to_text(name) for name, _ in loader.iter_modules(None)] if loader else []
 
 
@@ -528,7 +540,7 @@ class PkgutilMethod(FinderMethod):
             # then the containing package is imported.
             # Pre-'import spec' this returned None, in Python3.6 it raises
             # ImportError.
-            loader = pkgutil.find_loader(fullname)
+            loader = _find_loader(fullname)
         except ImportError:
             e = sys.exc_info()[1]
             LOG.debug('%r: find_loader(%r) failed: %s', self, fullname, e)
diff --git a/mitogen/parent.py b/mitogen/parent.py
index fa3092c1..f301a42c 100644
--- a/mitogen/parent.py
+++ b/mitogen/parent.py
@@ -1429,7 +1429,9 @@ class Connection(object):
             os.environ['ARGV0']=sys.executable
             os.execl(sys.executable,sys.executable+'(mitogen:CONTEXT_NAME)')
         os.write(1,'MITO000\n'.encode())
-        C=zlib.decompress(os.fdopen(0,'rb').read(PREAMBLE_COMPRESSED_LEN))
+        fp=os.fdopen(0,'rb')
+        C=zlib.decompress(fp.read(PREAMBLE_COMPRESSED_LEN))
+        fp.close()
         fp=os.fdopen(W,'wb',0)
         fp.write(C)
         fp.close()
diff --git a/tests/ansible/ansible.cfg b/tests/ansible/ansible.cfg
index 37edfd94..48a4eec3 100644
--- a/tests/ansible/ansible.cfg
+++ b/tests/ansible/ansible.cfg
@@ -10,6 +10,7 @@ callbacks_enabled =
 callback_whitelist =
     profile_tasks,
     timer
+duplicate_dict_key = error
 inventory = hosts
 gathering = explicit
 strategy_plugins = ../../ansible_mitogen/plugins/strategy
@@ -46,9 +47,13 @@ timeout = 30
 host_key_checking = False
 
 [inventory]
+# Fatal error if any inventory source is unparsed by every available plugin.
 any_unparsed_is_failed = true
+# Fatal error if no inventory sources have a match for a host pattern.
 host_pattern_mismatch = error
 ignore_extensions = ~, .bak, .disabled
+# Fatal error if no inventory sources are successfully parsed.
+unparsed_is_failed = true
 
 [callback_profile_tasks]
 task_output_limit = 10
diff --git a/tests/ansible/integration/runner/_reset_conn.yml b/tests/ansible/integration/runner/_reset_conn.yml
deleted file mode 100644
index 30f1b0c0..00000000
--- a/tests/ansible/integration/runner/_reset_conn.yml
+++ /dev/null
@@ -1,2 +0,0 @@
-
-- meta: reset_connection
diff --git a/tests/ansible/integration/transport_config/become.yml b/tests/ansible/integration/transport_config/become.yml
index 968d5e51..2f4fe37f 100644
--- a/tests/ansible/integration/transport_config/become.yml
+++ b/tests/ansible/integration/transport_config/become.yml
@@ -17,7 +17,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-become-unset
+- name: tc-become-unset via becomeuser@tc-become-set
+  hosts: tc-become-unset
   vars: {mitogen_via: becomeuser@tc-become-set}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -59,7 +60,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-become-set
+- name: tc-become-set via tc-become-unset
+  hosts: tc-become-set
   vars: {mitogen_via: tc-become-unset}
   become: true
   become_user: becomeuser
diff --git a/tests/ansible/integration/transport_config/become_method.yml b/tests/ansible/integration/transport_config/become_method.yml
index d6250314..0c2968eb 100644
--- a/tests/ansible/integration/transport_config/become_method.yml
+++ b/tests/ansible/integration/transport_config/become_method.yml
@@ -18,7 +18,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-become-method-unset
+- name: tc-become-method-unset via becomeuser@tc-become-method-su
+  hosts: tc-become-method-unset
   vars: {mitogen_via: becomeuser@tc-become-method-su}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -55,7 +56,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-become-method-su
+- name: tc-become-method-su via tc-become-method-unset
+  hosts: tc-become-method-su
   vars: {mitogen_via: tc-become-method-unset}
   become: true
   become_user: becomeuser
@@ -79,9 +81,9 @@
     - mitogen_only
 
 
-
 # mitogen_via used to specify explicit become method
-- hosts: tc-become-method-unset
+- name: tc-become-method-unset via doas:doasuser@tc-become-method-su
+  hosts: tc-become-method-unset
   vars: {mitogen_via: "doas:doasuser@tc-become-method-su"}
   tasks:
   - include_tasks: ../_mitogen_only.yml
diff --git a/tests/ansible/integration/transport_config/become_pass.yml b/tests/ansible/integration/transport_config/become_pass.yml
index c6b0fe72..d9a0bb55 100644
--- a/tests/ansible/integration/transport_config/become_pass.yml
+++ b/tests/ansible/integration/transport_config/become_pass.yml
@@ -79,7 +79,8 @@
 
 
 # ansible_become_password=, via=
-- hosts: tc-become-pass-password
+- name: tc-become-pass-password via root@tc-become-pass-pass
+  hosts: tc-become-pass-password
   vars: {mitogen_via: root@tc-become-pass-pass}
   become: true
   tasks:
@@ -119,7 +120,8 @@
 
 
 # ansible_become_pass=, via=
-- hosts: tc-become-pass-pass
+- name: tc-become-pass-pass via root@tc-become-pass-password
+  hosts: tc-become-pass-pass
   vars: {mitogen_via: root@tc-become-pass-password}
   become: true
   tasks:
@@ -161,7 +163,8 @@
 
 
 # both, mitogen_via
-- hosts: tc-become-pass-unset
+- name: tc-become-pass-unset via root@tc-become-pass-both
+  hosts: tc-become-pass-unset
   vars: {mitogen_via: root@tc-become-pass-both}
   tasks:
   - include_tasks: ../_mitogen_only.yml
diff --git a/tests/ansible/integration/transport_config/become_user.yml b/tests/ansible/integration/transport_config/become_user.yml
index 59dbe2a9..11c8abf8 100644
--- a/tests/ansible/integration/transport_config/become_user.yml
+++ b/tests/ansible/integration/transport_config/become_user.yml
@@ -79,7 +79,8 @@
 
 
 # ansible_become_user=, unbecoming via=
-- hosts: tc-become-user-set
+- name: tc-become-user-set via tc-become-user-unset
+  hosts: tc-become-user-set
   vars: {mitogen_via: tc-become-user-unset}
   become: true
   tasks:
@@ -103,7 +104,8 @@
 
 
 # ansible_become_user=, becoming via=
-- hosts: tc-become-user-set
+- name: tc-become-user-set via doas:doasuser@tc-become-user-unset
+  hosts: tc-become-user-set
   vars: {mitogen_via: "doas:doasuser@tc-become-user-unset"}
   become: true
   tasks:
diff --git a/tests/ansible/integration/transport_config/host_key_checking.yml b/tests/ansible/integration/transport_config/host_key_checking.yml
index 5f9c7e3a..d058531f 100644
--- a/tests/ansible/integration/transport_config/host_key_checking.yml
+++ b/tests/ansible/integration/transport_config/host_key_checking.yml
@@ -15,7 +15,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-hkc-unset
+- name: tc-hkc-unset via tc-hkc-host-key-checking
+  hosts: tc-hkc-unset
   vars:
     mitogen_via: tc-hkc-host-key-checking
   tasks:
@@ -48,7 +49,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-hkc-host-key-checking
+- name: tc-hkc-host-key-checking via tc-hkc-unset
+  hosts: tc-hkc-host-key-checking
   vars:
     mitogen_via: tc-hkc-unset
   tasks:
@@ -81,7 +83,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-hkc-ssh-host-key-checking
+- name: tc-hkc-ssh-host-key-checking via tc-hkc-unset
+  hosts: tc-hkc-ssh-host-key-checking
   vars:
     mitogen_via: tc-hkc-unset
   tasks:
diff --git a/tests/ansible/integration/transport_config/password.yml b/tests/ansible/integration/transport_config/password.yml
index c55939f7..5a1968e0 100644
--- a/tests/ansible/integration/transport_config/password.yml
+++ b/tests/ansible/integration/transport_config/password.yml
@@ -14,7 +14,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-password-unset
+- name: tc-password-unset via tc-password-explicit-ssh
+  hosts: tc-password-unset
   vars: {mitogen_via: tc-password-explicit-ssh}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -41,7 +42,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-password-explicit-ssh
+- name: tc-password-explicit-ssh via tc-password-unset
+  hosts: tc-password-explicit-ssh
   vars: {mitogen_via: tc-password-unset}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -68,7 +70,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-password-explicit-pass
+- name: tc-password-explicit-pass via tc-password-unset
+  hosts: tc-password-explicit-pass
   vars: {mitogen_via: tc-password-unset}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -95,7 +98,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-password-explicit-both
+- name: tc-password-explicit-both via tc-password-unset
+  hosts: tc-password-explicit-both
   vars: {mitogen_via: tc-password-unset}
   tasks:
   - include_tasks: ../_mitogen_only.yml
diff --git a/tests/ansible/integration/transport_config/port.yml b/tests/ansible/integration/transport_config/port.yml
index abc68058..6779f699 100644
--- a/tests/ansible/integration/transport_config/port.yml
+++ b/tests/ansible/integration/transport_config/port.yml
@@ -20,7 +20,8 @@
     - mitogen_only
 
 # Not set, mitogen_via=
-- hosts: tc-port-explicit-ssh
+- name: tc-port-explicit-ssh via tc-port-unset
+  hosts: tc-port-explicit-ssh
   vars: {mitogen_via: tc-port-unset}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -52,7 +53,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-port-unset
+- name: tc-port-unset via tc-port-explicit-ssh
+  hosts: tc-port-unset
   vars: {mitogen_via: tc-port-explicit-ssh}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -86,7 +88,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-port-unset
+- name: tc-port-unset via tc-port-explicit-port
+  hosts: tc-port-unset
   vars: {mitogen_via: tc-port-explicit-port}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -121,7 +124,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-port-unset
+- name: tc-port-unset via tc-port-both
+  hosts: tc-port-unset
   vars: {mitogen_via: tc-port-both}
   tasks:
   - include_tasks: ../_mitogen_only.yml
diff --git a/tests/ansible/integration/transport_config/python_path.yml b/tests/ansible/integration/transport_config/python_path.yml
index ecc24374..21f3928c 100644
--- a/tests/ansible/integration/transport_config/python_path.yml
+++ b/tests/ansible/integration/transport_config/python_path.yml
@@ -20,7 +20,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-python-path-hostvar
+- name: tc-python-path-hostvar via tc-python-path-unset
+  hosts: tc-python-path-hostvar
   vars: {mitogen_via: tc-python-path-unset}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -49,7 +50,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-python-path-unset
+- name: tc-python-path-unset via tc-python-path-hostvar
+  hosts: tc-python-path-unset
   vars: {mitogen_via: tc-python-path-hostvar}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -78,7 +80,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-python-path-unset
+- name: tc-python-path-unset via localhost
+  hosts: tc-python-path-unset
   vars: {mitogen_via: localhost}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -108,7 +111,8 @@
     - mitogen_only
 
 
-- hosts: localhost
+- name: localhost via tc-python-path-local-unset
+  hosts: localhost
   vars: {mitogen_via: tc-python-path-local-unset}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -134,7 +138,8 @@
   tags:
     - mitogen_only
 
-- hosts: localhost
+- name: localhost via tc-python-path-local-explicit
+  hosts: localhost
   vars: {mitogen_via: tc-python-path-local-explicit}
   tasks:
   - include_tasks: ../_mitogen_only.yml
diff --git a/tests/ansible/integration/transport_config/remote_addr.yml b/tests/ansible/integration/transport_config/remote_addr.yml
index b1a6c5a7..9f7ff5f6 100644
--- a/tests/ansible/integration/transport_config/remote_addr.yml
+++ b/tests/ansible/integration/transport_config/remote_addr.yml
@@ -15,7 +15,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-remote-addr-unset
+- name: tc-remote-addr-unset via tc-remote-addr-explicit-ssh
+  hosts: tc-remote-addr-unset
   vars: {mitogen_via: tc-remote-addr-explicit-ssh}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -42,7 +43,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-remote-addr-explicit-ssh
+- name: tc-remote-addr-explicit-ssh via tc-remote-addr-unset
+  hosts: tc-remote-addr-explicit-ssh
   vars: {mitogen_via: tc-remote-addr-unset}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -69,7 +71,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-remote-addr-explicit-host
+- name: tc-remote-addr-explicit-host via tc-remote-addr-unset
+  hosts: tc-remote-addr-explicit-host
   vars: {mitogen_via: tc-remote-addr-unset}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -96,7 +99,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-remote-addr-explicit-both
+- name: tc-remote-addr-explicit-both via tc-remote-addr-unset
+  hosts: tc-remote-addr-explicit-both
   vars: {mitogen_via: tc-remote-addr-unset}
   tasks:
   - include_tasks: ../_mitogen_only.yml
diff --git a/tests/ansible/integration/transport_config/remote_user.yml b/tests/ansible/integration/transport_config/remote_user.yml
index a5559edb..94fcf485 100644
--- a/tests/ansible/integration/transport_config/remote_user.yml
+++ b/tests/ansible/integration/transport_config/remote_user.yml
@@ -16,7 +16,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-remote-user-unset
+- name: tc-remote-user-unset via tc-remote-user-explicit-ssh
+  hosts: tc-remote-user-unset
   vars: {mitogen_via: tc-remote-user-explicit-ssh}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -43,7 +44,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-remote-user-explicit-ssh
+- name: tc-remote-user-explicit-ssh via tc-remote-user-unset
+  hosts: tc-remote-user-explicit-ssh
   vars: {mitogen_via: tc-remote-user-unset}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -68,7 +70,8 @@
       left: out.result[0].kwargs.username
       right: "ansi-user"
 
-- hosts: tc-remote-user-explicit-user
+- name: tc-remote-user-explicit-user via tc-remote-user-unset
+  hosts: tc-remote-user-explicit-user
   vars: {mitogen_via: tc-remote-user-unset}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -95,7 +98,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-remote-user-explicit-both
+- name: tc-remote-user-explicit-both via tc-remote-user-unset
+  hosts: tc-remote-user-explicit-both
   vars: {mitogen_via: tc-remote-user-unset}
   tasks:
   - include_tasks: ../_mitogen_only.yml
diff --git a/tests/ansible/integration/transport_config/transport.yml b/tests/ansible/integration/transport_config/transport.yml
index 1bac788b..0b0568e8 100644
--- a/tests/ansible/integration/transport_config/transport.yml
+++ b/tests/ansible/integration/transport_config/transport.yml
@@ -14,7 +14,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-transport-local
+- name: tc-transport-local via tc-transport-unset
+  hosts: tc-transport-local
   vars: {mitogen_via: tc-transport-unset}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -41,7 +42,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-transport-unset
+- name: tc-transport-unset via tc-transport-local
+  hosts: tc-transport-unset
   vars: {mitogen_via: tc-transport-local}
   tasks:
   - include_tasks: ../_mitogen_only.yml
diff --git a/tests/ansible/integration/transport_config/transport__smart.yml b/tests/ansible/integration/transport_config/transport__smart.yml
index d2adca45..2ed513af 100644
--- a/tests/ansible/integration/transport_config/transport__smart.yml
+++ b/tests/ansible/integration/transport_config/transport__smart.yml
@@ -15,7 +15,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-transport-local
+- name: tc-transport-local via tc-transport-smart
+  hosts: tc-transport-local
   vars: {mitogen_via: tc-transport-smart}
   tasks:
   - include_tasks: ../_mitogen_only.yml
@@ -42,7 +43,8 @@
   tags:
     - mitogen_only
 
-- hosts: tc-transport-smart
+- name: tc-transport-smart via tc-transport-local
+  hosts: tc-transport-smart
   vars: {mitogen_via: tc-transport-local}
   tasks:
   - include_tasks: ../_mitogen_only.yml
diff --git a/tests/ansible/tests/connection_test.py b/tests/ansible/tests/connection_test.py
index 649f8b65..856c6b1c 100644
--- a/tests/ansible/tests/connection_test.py
+++ b/tests/ansible/tests/connection_test.py
@@ -45,7 +45,9 @@ class ConnectionMixin(MuxProcessMixin):
         conn = self.klass(play_context, new_stdin=False)
         # conn functions don't fetch ActionModuleMixin objs from _get_task_vars()
         # through the usual walk-the-stack approach so we'll not run interpreter discovery here
-        conn._action = mock.MagicMock(_possible_python_interpreter=testlib.base_executable())
+        conn._action = mock.MagicMock(
+            _mitogen_interpreter_candidate=testlib.base_executable(),
+        )
         conn.on_action_run(
             task_vars={},
             delegate_to_hostname=None,
diff --git a/tests/data/fd_check.py b/tests/data/fd_check.py
index 0a87a95e..f3684443 100755
--- a/tests/data/fd_check.py
+++ b/tests/data/fd_check.py
@@ -26,6 +26,7 @@ def controlling_tty():
         return None
 
 
+out_path = sys.argv[1]
 fd = int(sys.argv[2])
 st = os.fstat(fd)
 
@@ -35,7 +36,7 @@ if sys.argv[3] == 'write':
 else:
     buf = os.read(fd, 4).decode()
 
-open(sys.argv[1], 'w').write(repr({
+output = repr({
     'buf': buf,
     'flags': fcntl.fcntl(fd, fcntl.F_GETFL),
     'st_mode': st.st_mode,
@@ -43,4 +44,21 @@ open(sys.argv[1], 'w').write(repr({
     'st_ino': st.st_ino,
     'ttyname': ttyname(fd),
     'controlling_tty': controlling_tty(),
-}))
+})
+
+try:
+    out_f = open(out_path, 'w')
+except Exception:
+    exc = sys.exc_info()[1]
+    sys.stderr.write("Failed to open %r: %r" % (out_path, exc))
+    sys.exit(1)
+
+try:
+    out_f.write(output)
+except Exception:
+    out_f.close()
+    exc = sys.exc_info()[1]
+    sys.stderr.write("Failed to write to %r: %r" % (out_path, exc))
+    sys.exit(2)
+
+out_f.close()
diff --git a/tox.ini b/tox.ini
index ea988aa0..bd2d65e9 100644
--- a/tox.ini
+++ b/tox.ini
@@ -105,6 +105,8 @@ setenv =
     NOCOVERAGE_ERASE = 1
     NOCOVERAGE_REPORT = 1
     PIP_CONSTRAINT={toxinidir}/tests/constraints.txt
+    # Print warning on the first occurence at each module:linenno in Mitogen. Available Python 2.7, 3.2+.
+    PYTHONWARNINGS=default:::ansible_mitogen,default:::mitogen
     # Ansible 6 - 8 (ansible-core 2.13 - 2.15) require Python 2.7 or >= 3.5 on targets
     ansible6: MITOGEN_TEST_DISTRO_SPECS=centos7 centos8 debian9 debian10 debian11 ubuntu1604 ubuntu1804 ubuntu2004
     ansible7: MITOGEN_TEST_DISTRO_SPECS=centos7 centos8 debian9 debian10 debian11 ubuntu1604 ubuntu1804 ubuntu2004
@@ -140,7 +142,6 @@ allowlist_externals =
     # Added: Tox 3.18: Tox 4.0+
     *_install.py
     *_tests.py
-    aws
     docker
     docker-credential-secretservice
     echo
@@ -150,7 +151,6 @@ whitelist_externals =
     # Deprecated: Tox 3.18+; Removed: Tox 4.0
     *_install.py
     *_tests.py
-    aws
     docker
     docker-credential-secretservice
     echo