Assertion rewriting breaks jedi due to missing InspectLoader support

[iwanb]

platform linux -- Python 3.7.6, pytest-5.3.4, py-1.6.0, pluggy-0.12.0

I am using IPython with jedi completions within a pytest session. Assertion rewriting is enabled, but doing completions on rewritten modules crashes jedi because mod.__loader__.is_package is not implemented.
https://docs.python.org/3/library/importlib.html#importlib.abc.InspectLoader

AFAIK is would be best if the importer subclass those:
https://docs.python.org/3/library/importlib.html#importlib.abc.FileLoader
https://docs.python.org/3/library/importlib.html#importlib.abc.SourceLoader

To get all the methods implemented.

See the trace at davidhalter/jedi#1487

This is probably related to #3919 where is_package was removed.

[RonnyPfannschmidt]

as by now the mainline no longer supports python 2,
i think we can investigate sorting this out by using more of importlib

thanks for bringing this up

[blueyed]

This is probably related to #3919 where is_package was removed.

It was removed in 4cd08f9 (#5468).
Not sure if bug or enhancement though. (btw: the Jedi issue was fixed already)