[3.7] bpo-33169: Remove values of `None` from sys.path_importer_cache when invalidating caches (GH-6402) by brettcannon · Pull Request #6403

[3.7] bpo-33169: Remove values of `None` from sys.path_importer_cache when invalidating caches (GH-6402) by brettcannon · Pull Request #6403 · python/cpython

… when invalidating caches (pythonGH-6402)

An entry of None in sys.path_importer_cache represents a negative/missing finder for a path, so clearing it out makes sense..
(cherry picked from commit 9e2be60)

Co-authored-by: Brett Cannon <brettcannon@users.noreply.github.com>