Add note in documentation to help modernize code bases to use pathlib

[sgaist]

The legacypath plugin handles the tmpdir and tmpdir_factory which should be update to their modern counterparts that uses pathlib.

Disabling this plugin allows developer to easily find and thus update the use of these fixtures.

Fixes #10199

[nicoddemus]

Shouldn't this be just -p no:legacypath?

[sgaist]

Good question

I used the registered name defined in legacypath.py.

From a quick test:

def test_tmpdir(tmpdir):
      assert True
def test_tmpdir_factory(tmpdir_factory):
      assert True

either no:legacypath or no:legacypath-tmpdir triggers the expected error.

However, using pytest --trace-config, legacypath is listed there, so you are correct.

I will correct that.

[nicoddemus]

Thanks!

[nicoddemus]

@bluetech the backport workflow failed with:

HTTP 401: Bad credentials (https://api.github.com/graphql)

This is not supercritical to port right now, just mentioned in case you were not aware.