xdist does not work with --assert=plain

[punitchandra]

Running
pytest --doctest-modules -v --assert=plain
works without assert rewriting.

Running
pytest --doctest-modules -v --assert=plain -n 2
is still doing the assert rewriting.

I have to use --assert=plain as the tests are using pickle and assert rewriting is creating problems with pickle. Specifically it tries to pickle typing.io which does not support pickling.

[nicoddemus]

Hi @punitchandra, thanks for the report.

It seems the problem is that _consider_import_hook requires the --assert=plain option in the command-line, but workers don't receive the command-line parameters, only the filenames... not sure how to fix this.

[nicoddemus]

@RonnyPfannschmidt is this related to pytest-dev/pytest#3376?

[RonnyPfannschmidt]

@nicoddemus not yet, but its yet another reason why the detangle is needed

[simon-weber]

This also relates to #353: it's not currently possible to disable assertion rewriting for performance reasons.

I was surprised to see that setting PYTHONDONTWRITEBYTECODE didn't work either. I'll look into adding that to _consider_import_hook.