This is a tracker issue for running and PR-ing automated refactors using pyupgrade, per #9131.

I'll do this in the following changes:

• Remove all # -*- coding: utf-8 -*- lines (Remove redundant "coding: utf-8" lines #9786)
• pyupgrade the codebase with --keep-precent-format
  • tests/ ([pyupgrade] tests/ #10347)
  • synapse/ ([pyupgrade] synapse/ #10348)
  • Other (#XXXX)
• pyupgrade without --keep-precent-format (#XXXX)

Overall Extra Info

Some common changes from pyupgrade:

• Changes %-formatting to .format (or f-strings if non-trivial)
• Removes coding: utf-8 file header (not needed since python 3)
• Changes typing.TypedDict("A") class instantiations to class A(TypedDict)