Pin parso to 0.8.1 for compartibility with jedi 0.18.0

[dominiquesydow]

CI / docs fails (example):

Exception occurred:
  File "/usr/share/miniconda/envs/test/lib/python3.8/site-packages/pkg_resources/__init__.py", line 790, in resolve
    raise VersionConflict(dist, req).with_context(dependent_req)
pkg_resources.ContextualVersionConflict: (parso 0.7.1 (/usr/share/miniconda/envs/test/lib/python3.8/site-packages), Requirement.parse('parso<0.9.0,>=0.8.0'), {'jedi'})
The full traceback has been saved in /tmp/sphinx-err-tn7knlux.log, if you want to report the issue to the developers.

[Dismissed] As far as I understand this happens because the latest jedi version (0.18.0) is not compatible with the latest ipython version (7.19.0). This is described here alongside a workaround until a new ipython version is released with a fix: https://github.com/ipython/ipython/issues/12740

Taking the ContextualVersionConflict information more seriously, our problem can be fixed by pinning parso to version 0.8.1. Still unsure which package co-installs parso 0.7.1 and jedi 0.18.0.

TODOs:

• [x] [Dismissed] Pin jedi to 0.17.2 (not sure yet where - try out after/before ipython in test_env.yaml?)
• [x] Pin parso to 0.8.1
• [ ] Remove fix from test_env.yaml when it becomes more clear who causes this problem

[dominiquesydow]

Could reproduce the ContextualVersionConflict now locally. Upgrading parso to 0.8.1 solved the problem.

Unsure who installs parso and jedi in our environment - sphinx? Looking into this.

Maybe our problem is not related to the ipython problem mentioned before.

[dominiquesydow]

Not needed anymore.