[stable-2.9] Fix ansible-test virtualenv real python search.

ansible-test now properly searches for `pythonX.Y` instead of `python` when looking for the real python that created a `virtualenv`.
(cherry picked from commit b91f452f4f)

Co-authored-by: Matt Clay <matt@mystile.com>

changelogs/fragments/ansible-test-virtualenv-python-search.yml

@@ -0,0 +1,2 @@
+bugfixes:
+    - ansible-test now properly searches for ``pythonX.Y`` instead of ``python`` when looking for the real python that created a ``virtualenv``

test/lib/ansible_test/_internal/venv.py

@@ -4,6 +4,7 @@ __metaclass__ = type
 
 import json
 import os
+import sys
 
 from . import types as t
 
@@ -46,9 +47,13 @@ def create_virtual_environment(args,  # type: EnvironmentConfig
 
     if python_version >= (3, 0):
         # use the built-in 'venv' module on Python 3.x
-        if run_venv(args, python, system_site_packages, pip, path):
-            display.info('Created Python %s virtual environment using "venv": %s' % (version, path), verbosity=1)
-            return True
+        # creating a virtual environment using 'venv' when running in a virtual environment created by 'virtualenv' results
+        # in a copy of the original virtual environment instead of creation of a new one
+        # avoid this issue by only using "real" python interpreters to invoke 'venv'
+        for real_python in iterate_real_pythons(args, version):
+            if run_venv(args, real_python, system_site_packages, pip, path):
+                display.info('Created Python %s virtual environment using "venv": %s' % (version, path), verbosity=1)
+                return True
 
         # something went wrong, most likely the package maintainer for the Python installation removed ensurepip
         # which will prevent creation of a virtual environment without installation of other OS packages
@@ -80,6 +85,56 @@ def create_virtual_environment(args,  # type: EnvironmentConfig
     return False
 
 
+def iterate_real_pythons(args, version):  # type: (EnvironmentConfig, str) -> t.Iterable[str]
+    """
+    Iterate through available real python interpreters of the requested version.
+    The current interpreter will be checked and then the path will be searched.
+    """
+    version_info = tuple(int(n) for n in version.split('.'))
+    current_python = None
+
+    if version_info == sys.version_info[:len(version_info)]:
+        current_python = sys.executable
+        real_prefix = get_python_real_prefix(args, current_python)
+
+        if real_prefix:
+            current_python = find_python(version, os.path.join(real_prefix, 'bin'))
+
+        if current_python:
+            yield current_python
+
+    path = os.environ.get('PATH', os.path.defpath)
+
+    if not path:
+        return
+
+    found_python = find_python(version, path)
+
+    if not found_python:
+        return
+
+    if found_python == current_python:
+        return
+
+    real_prefix = get_python_real_prefix(args, found_python)
+
+    if real_prefix:
+        found_python = find_python(version, os.path.join(real_prefix, 'bin'))
+
+    if found_python:
+        yield found_python
+
+
+def get_python_real_prefix(args, path):  # type: (EnvironmentConfig, str) -> t.Optional[str]
+    """
+    Return the real prefix of the specified interpreter or None if the interpreter is not a virtual environment created by 'virtualenv'.
+    """
+    cmd = [path, os.path.join(os.path.join(ANSIBLE_TEST_DATA_ROOT, 'virtualenvcheck.py'))]
+    check_result = json.loads(run_command(args, cmd, capture=True, always=True)[0])
+    real_prefix = check_result['real_prefix']
+    return real_prefix
+
+
 def run_venv(args,  # type: EnvironmentConfig
              run_python,  # type: str
              system_site_packages,  # type: bool
@@ -87,15 +142,6 @@ def run_venv(args,  # type: EnvironmentConfig
              path,  # type: str
              ):  # type: (...) -> bool
     """Create a virtual environment using the 'venv' module. Not available on Python 2.x."""
-    cmd = [run_python, os.path.join(os.path.join(ANSIBLE_TEST_DATA_ROOT, 'virtualenvcheck.py'))]
-    check_result = json.loads(run_command(args, cmd, capture=True, always=True)[0])
-    real_prefix = check_result['real_prefix']
-
-    if real_prefix:
-        # we must use the real python to create a virtual environment with venv
-        # attempting to use python from a virtualenv created virtual environment results in a copy of that environment instead
-        run_python = os.path.join(real_prefix, 'bin', 'python')
-
     cmd = [run_python, '-m', 'venv']
 
     if system_site_packages: