feat(client): automatically retry on HTTP 409 Resource lock

[pspacek]

Fixes: #2325

[lmilbaum]

Unit tests might increase the confidence that the code is working as expected. Would you mind adding unit tests?

[nejch]

@pspacek thanks for the quick work here! Just a few nits.

Regarding unit tests and your question in #2325 (comment).

We have some vendored code from httmock for a similar reason (redirects). I think you might be able to reuse it here?
https://github.com/python-gitlab/python-gitlab/blob/main/tests/unit/helpers.py

See how it's used in the redirect tests:
https://github.com/python-gitlab/python-gitlab/blob/main/tests/unit/test_gitlab_http_methods.py#L310-L317

Let us know if you need help with that :) That's a shame about responses though.

[nejch]

And @pspacek we're also ok to go ahead without the unit tests if it's too complicated and we open a follow-up issue to resolve on our end :)

[nejch]

Hi @pspacek! Let us know if you'd like to finish this PR, or if we should push to your branch to get this merged (either way you'll be credited as the commit author). Thanks again for the contribution!

[pspacek]

@nejch I'm sorry, I have no time to work on this. Feel free to do whatever you like.

[nejch]

We're mostly doing this because responses doesn't support mocking Response.reason as @pspacek already found out in #2325 (comment).

[nejch]

This LGTM but I added a commit in 25446cf to finish the PR so will need someone else to do the merge.

Thanks again @pspacek!

[codecov-commenter]

Codecov Report

Merging #2326 (1a37bab) into main (c7cf0d1) will increase coverage by 0.00%.
The diff coverage is 90.90%.

@@           Coverage Diff           @@
##             main    #2326   +/-   ##
=======================================
  Coverage   96.13%   96.13%           
=======================================
  Files          84       85    +1     
  Lines        5534     5569   +35     
=======================================
+ Hits         5320     5354   +34     
- Misses        214      215    +1     

Flag	Coverage Δ
api_func_v4	82.58% <54.54%> (+<0.01%)	⬆️
cli_func_v4	82.83% <45.45%> (-0.06%)	⬇️
unit	87.48% <81.81%> (+0.04%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
gitlab/client.py	98.38% <90.90%> (-0.18%)	⬇️
gitlab/v4/objects/__init__.py	100.00% <0.00%> (ø)
gitlab/v4/objects/resource_groups.py	100.00% <0.00%> (ø)
gitlab/v4/objects/projects.py	98.86% <0.00%> (+<0.01%)	⬆️

[nejch]

Unit tests might increase the confidence that the code is working as expected. Would you mind adding unit tests?

@lmilbaum I've added a commit on top of the author's to rework and add tests (1a37bab). Maybe you can take a look and we can merge before the next release.

[lmilbaum]

LGTM