Revise tests that rely on importlib.reload

[matthewfeickert]

Description

RE: pyhf related Stack Overflow question "How to remove a library with monkeypatch or mock in pytest?" which was used to write tests for missing extra dependencies from the contrib extra, @asottile has warned that

reload() can be kinda iffy -- I'd be careful with it (things which have old references to the old module will live on, sometimes it can introduce new copies of singletons (doubletons? tripletons?)) -- I've tracked down many-a-test-pollution problems to reload()

It would be good to look into if there are more reasonable ways to force the reload of the relevant modules to trigger the import error.

In his video testing optional python dependencies (intermediate) Anthony demos using mock.patch.object to patch the imported dependency in the module where it is imported. I think there was some reason I didn't end up doing this for the PR in which contrib download was added, but I can't remember why (maybe because I wanted a specific import error?) so this is probably a good place to start revisiting the Issue.

This comes up in the context of:

• PR feat: Add API to download likelihood patchset archives #1046
• PR refactor: Migrate contrib download to contrib module #1119