[module_utils.distro] Fall back to bundled (#74229)

Change:
- When a "distro" package exists in PYTHONPATH but isn't what we expect,
  fall back to our own vendored one and use it. This prevents a
  traceback if someone has some random thing that provides "distro" but
  isn't actually the "distro" library we need.

Test Plan:
- new tests

Tickets:
- Fixes #74228

Signed-off-by: Rick Elrod <rick@elrod.me>

* nuke playbook test file

Signed-off-by: Rick Elrod <rick@elrod.me>

* test fixes

Signed-off-by: Rick Elrod <rick@elrod.me>

changelogs/fragments/nonstandard-distro-fallback.yml

@@ -0,0 +1,2 @@
+minor_changes:
+  - module_utils distro - when a 'distro' package/module is in PYTHONPATH but isn't the real 'distro' package/module that we expect, gracefully fall back to our own bundled distro.

lib/ansible/module_utils/distro/__init__.py

@@ -32,15 +32,25 @@ _BUNDLED_METADATA = {"pypi_name": "distro", "version": "1.5.0"}
 
 
 import sys
+import types
 
 try:
     import distro as _system_distro
 except ImportError:
     _system_distro = None
+else:
+    # There could be a 'distro' package/module that isn't what we expect, on the
+    # PYTHONPATH. Rather than erroring out in this case, just fall back to ours.
+    # We require more functions than distro.id(), but this is probably a decent
+    # test that we have something we can reasonably use.
+    if not hasattr(_system_distro, 'id') or \
+       not isinstance(_system_distro.id, types.FunctionType):
+        _system_distro = None
 
 if _system_distro:
     distro = _system_distro
 else:
     # Our bundled copy
     from ansible.module_utils.distro import _distro as distro
+
 sys.modules['ansible.module_utils.distro'] = distro

test/integration/targets/module_utils_distro/aliases

@@ -0,0 +1 @@
+shippable/posix/group3

test/integration/targets/module_utils_distro/meta/main.yml

@@ -0,0 +1,2 @@
+dependencies:
+  - setup_remote_tmp_dir

test/integration/targets/module_utils_distro/runme.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+
+set -eux
+
+# Ensure that when a non-distro 'distro' package is in PYTHONPATH, we fallback
+# to our bundled one.
+new_pythonpath="$OUTPUT_DIR/pythonpath"
+mkdir -p "$new_pythonpath/distro"
+touch "$new_pythonpath/distro/__init__.py"
+
+export PYTHONPATH="$new_pythonpath:$PYTHONPATH"
+
+# Sanity test to make sure the above worked
+set +e
+distro_id_fail="$(python -c 'import distro; distro.id' 2>&1)"
+set -e
+grep -q "AttributeError:.*has no attribute 'id'" <<< "$distro_id_fail"
+
+# ansible.module_utils.common.sys_info imports distro, and itself gets imported
+# in DataLoader, so all we have to do to test the fallback is run `ansible`.
+ansirun="$(ansible -i ../../inventory -a "echo \$PYTHONPATH" localhost)"
+grep -q "$new_pythonpath" <<< "$ansirun"
+
+rm -rf "$new_pythonpath"