bpo-38691: importlib ignores PYTHONCASEOK if -E is used (GH-18627)

The importlib module now ignores the PYTHONCASEOK
environment variable when the -E or -I command line
options are being used.
diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index ca09e6f..3474216 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -1835,6 +1835,9 @@
       Negative values for *level* are no longer supported (which also changes
       the default value to 0).
 
+   .. versionchanged:: 3.9
+      When the command line options :option:`-E` or :option:`-I` are being used,
+      the environment variable :envvar:`PYTHONCASEOK` is now ignored.
 
 .. rubric:: Footnotes