chore(python): Issue a warning when running doctests on Python 3.11 o…

…r lower (#14187)

py-polars/tests/docs/run_doctest.py

@@ -43,6 +43,16 @@
     from types import ModuleType
 
 
+if sys.version_info < (3, 12):
+    # Tests that print an OrderedDict fail (e.g. DataFrame.schema) as the repr
+    # has changed in Python 3.12
+    warnings.warn(
+        "Certain doctests may fail when running on a Python version below 3.12."
+        " Update your Python version to 3.12 or later to make sure all tests pass.",
+        stacklevel=2,
+    )
+
+
 def doctest_teardown(d: doctest.DocTest) -> None:
     # don't let config changes or string cache state leak between tests
     polars.Config.restore_defaults()