Issues running pytest from within .pybuild

[Christian Kastner <ckk@debian.org>]

In a recent version of src:scikit-learn, a workaround was added to
resolve an ImportMismatchError regarding one of the conftest.py files
used by pytest.

I hit a new instance of this while preparing a new upstream release, so
I inquired [1] with pytest upstream as to why this could be happening.

Apparently, the error is caused by the .pybuild directory being located
as a subfolder of the source directory. This leads to pytest finding two
separate sklearn/conftest.py files
  * $SRCDIR/sklearn/conftest.py
  * $SRCDIR/.pybuild/.../sklearn/conftest.py)
which triggers the ImportMisMatchError.

Now, I've only seen this happen with src:scikit-learn, and (oddly
enough) only with 2 of 4 conftest.py files. The other two do not trigger
the error, nor do other packages of mine which use pytest.

Has anyone seen something similar with their packages, or is anyone
aware of any recipes that can be used to resolve the issue properly?

>From the GitHub issue, it seems as if the current practice of testing
from within .pybuild is not supported by pytest, but I'm inclined to
believe that it is my approach that is flawed.

[1] https://github.com/pytest-dev/pytest/issues/7223

Christian