[stable-2.17] ansible-test - Improve unknown env error message (#83677)

(cherry picked from commit 906c969b55)

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

changelogs/fragments/ansible-test-error-message-improvement.yml

@@ -0,0 +1,2 @@
+minor_changes:
+  - ansible-test - Improve the error message shown when an unknown ``--remote`` or ``--docker`` option is given.

test/lib/ansible_test/_internal/cli/compat.py

@@ -93,7 +93,10 @@ class PythonVersionUnspecifiedError(ApplicationError):
     """A Python version was not specified for a context which is unknown, thus the Python version is unknown."""
 
     def __init__(self, context: str) -> None:
-        super().__init__(f'A Python version was not specified for environment `{context}`. Use the `--python` option to specify a Python version.')
+        super().__init__(
+            f'Environment `{context}` is unknown. Use a predefined environment instead. '
+            f'Alternatively, to use an unknown environment, use the `--python` option to specify a Python version.'
+        )
 
 
 class ControllerNotSupportedError(ApplicationError):