[3.8] bpo-39299: Add more tests for mimetypes and its cli. (GH-17949)#17992

miss-islington merged 1 commit intopython:3.8python/cpython:3.8from

miss-islington:backport-d8efc14-3.8miss-islington/cpython:backport-d8efc14-3.8Copy head branch name to clipboard