Update to Mypy 0.910

[Dreamsorcerer]

No description provided.

[codecov]

Codecov Report

Merging #5890 (bf13421) into master (e3dcc71) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #5890   +/-   ##
=======================================
  Coverage   96.75%   96.75%           
=======================================
  Files          44       44           
  Lines        9851     9851           
  Branches     1591     1591           
=======================================
  Hits         9531     9531           
  Misses        182      182           
  Partials      138      138           

Flag	Coverage Δ
unit	96.65% <ø> (ø)

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[patchback]

Backport to 3.8: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply ae23fd6 on top of patchback/backports/3.8/ae23fd6a1645eacaf63d64c638f19310282d07b9/pr-5890

Backporting merged PR #5890 into master

1. Ensure you have a local repo clone of your fork. Unless you cloned it
   from the upstream, this would be your origin remote.
2. Make sure you have an upstream repo added as a remote too. In these
   instructions you'll refer to it by the name upstream. If you don't
   have it, here's how you can add it:

   $ git remote add upstream https://github.com/aio-libs/aiohttp.git

3. Ensure you have the latest copy of upstream and prepare a branch
   that will hold the backported code:

   $ git fetch upstream
   $ git checkout -b patchback/backports/3.8/ae23fd6a1645eacaf63d64c638f19310282d07b9/pr-5890 upstream/3.8

4. Now, cherry-pick PR Update to Mypy 0.910 #5890 contents into that branch:

   $ git cherry-pick -x ae23fd6a1645eacaf63d64c638f19310282d07b9

   If it'll yell at you with something like fatal: Commit ae23fd6a1645eacaf63d64c638f19310282d07b9 is a merge but no -m option was given., add -m 1 as follows intead:

   $ git cherry-pick -m1 -x ae23fd6a1645eacaf63d64c638f19310282d07b9

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Update to Mypy 0.910 #5890 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.8/ae23fd6a1645eacaf63d64c638f19310282d07b9/pr-5890

7. Create a PR, ensure that the CI is green. If it's not — update it so that
   the tests and any other checks pass. This is it!
   Now relax and wait for the maintainers to process your pull request
   when they have some cycles to do reviews. Don't worry — they'll tell you if
   any improvements are necessary when the time comes!

🤖 @patchback
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