[3.8] bpo-13487: Use sys.modules.copy() in inspect.getmodule() for thread safety. (GH-18786) by miss-islington · Pull Request #18787

[3.8] bpo-13487: Use sys.modules.copy() in inspect.getmodule() for thread safety. (GH-18786) by miss-islington · Pull Request #18787 · python/cpython

…afety. (pythonGH-18786)

`list(sys.modules.items())` was apparently not immune to "dictionary
changed size during iteration" errors.

Tested internally using an integration test that has run into this a couple of times in the past two years.  With this patch applied, the test is no longer flaky.
(cherry picked from commit 85cf1d5)

Co-authored-by: Gregory P. Smith <gps@google.com>