cache_tests needs 5-7 minutes for each instance to run on CI (Github or Appveyor):
Log entry (Python 3.9):
[00:19:09] Test the apicache by doing _check_cache_entry over each entry. ... 306.628s ok
Log entry (Python 3.6):
[00:29:45] Test the apicache by doing _check_cache_entry over each entry. ... 398.695s ok