Deprecate Python 2 relic --no-python-version-warning

Author: ichard26

news/13154.removal.rst

@@ -0,0 +1,2 @@
+Deprecate the ``no-python-version-warning`` flag as it has long done nothing
+since Python 2 support was removed in pip 21.0.

src/pip/_internal/cli/base_command.py

@@ -29,6 +29,7 @@
     NetworkConnectionError,
     PreviousBuildDirError,
 )
+from pip._internal.utils.deprecation import deprecated
 from pip._internal.utils.filesystem import check_path_owner
 from pip._internal.utils.logging import BrokenStdoutLoggingError, setup_logging
 from pip._internal.utils.misc import get_prog, normalize_path
@@ -228,4 +229,12 @@ def _main(self, args: List[str]) -> int:
                 )
                 options.cache_dir = None
 
+        if options.no_python_version_warning:
+            deprecated(
+                reason="--no-python-verison-warning is deprecated.",
+                replacement="to remove the flag as it's a no-op",
+                gone_in="25.1",
+                issue=13154,
+            )
+
         return self._run_wrapper(level_number, options, args)