Use pytest-aiohttp in tests

[hroncok]

Otherwise, we get:

E fixture 'aiohttp_client' not found

What do these changes do?

Add a test dependency on pytest-aiohttp.

Are there changes in behavior for the user?

No. Tests only.

Related issue number

I haven't opened one.

Checklist

• I think the code is well written
• Unit tests for the changes exist - without his, the tests won't run
• Documentation reflects the changes - not needed
• Add a new news fragment into the CHANGES folder
  • name it <issue_id>.<type> (e.g. 588.bugfix)
  • if you don't have an issue_id change it to the pr id after creating the PR
  • ensure type is one of the following:
    • .feature: Signifying a new feature.
    • .bugfix: Signifying a bug fix.
    • .doc: Signifying a documentation improvement.
    • .removal: Signifying a deprecation or removal of public API.
    • .misc: A ticket has been closed, but it is not of interest to users.
  • Make sure to use full sentences with correct case and punctuation, for example: Fix issue with non-ascii contents in doctest text files.

There is no CHANGES folder.

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[hroncok]

This is not a nice response to a PR after 1 year. Consider my contribution Public Domain.

[JulienPalard]

I tested this PR and it correctly fixes pytest.PytestUnhandledCoroutineWarning: async def functions are not natively supported and have been skipped., it should be mergd.