task idea: Remove unused imports from files

[hackerkid]

We have a lot of unused import in many python files. Removing them can be a task.

[rht]

This had been finished in zulip/zulip#7262 actually. I ran flake8 and grepped for F401, while making sure that the ones needed by type annotation (in Python 2 syntax) are still imported.

[timabbott]

@rht did that actually cover the whole codebase? I would have thought it's only done for the parts of the codebase that we've moved to the Python 3 type syntax...

[rht]

Yup, I updated the statement here: zulip/zulip#7262 (comment). This can be quickly re-verified later anyway once the full mypy comments to annotations migration has been completed.