declare "allow_cache_wipe" marker in pytest.ini to avoid pytest warning

[FelixSchwarz]

Undeclared markers trigger a pytest warning:
PytestUnknownMarkWarning: Unknown pytest.mark.allow_cache_wipe - is this a typo?

You can see the warning in the current travis output:

=============================== warnings summary ===============================

.tox/py38/lib/python3.8/site-packages/borg/testsuite/archiver.py:1726

  /home/travis/build/borgbackup/borg/.tox/py38/lib/python3.8/site-packages/borg/testsuite/archiver.py:1726: PytestUnknownMarkWarning: Unknown pytest.mark.allow_cache_wipe - is this a typo?  You can register custom marks to avoid this warning - for details, see https://docs.pytest.org/en/latest/mark.html

    @pytest.mark.allow_cache_wipe

-- Docs: https://docs.pytest.org/en/latest/warnings.html

[ThomasWaldmann]

travis-ci looks rather unhappy somehow.

[ThomasWaldmann]

this does not run any tests any more.

[ThomasWaldmann]

guess moving this to the pytest section in setup.cfg would fix it.

[FelixSchwarz]

@ThomasWaldmann sorry for just dumping this PR. Your guess was correct. I pushed an updated version of this commit.

[codecov-commenter]

Codecov Report

Merging #5197 into master will decrease coverage by 0.16%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #5197      +/-   ##
==========================================
- Coverage   84.06%   83.90%   -0.17%     
==========================================
  Files          37       37              
  Lines        9836     9836              
  Branches     1638     1638              
==========================================
- Hits         8269     8253      -16     
- Misses       1090     1103      +13     
- Partials      477      480       +3     

Impacted Files	Coverage Δ
src/borg/archive.py	82.76% <0.00%> (-0.62%)	⬇️
src/borg/archiver.py	81.03% <0.00%> (-0.36%)	⬇️

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[ThomasWaldmann]

guess this is also needed for 1.1-maint?

[FelixSchwarz]

guess this is also needed for 1.1-maint?

Well, the problem also applies to 1.1.x but for me it is not important to fix because it is just a warning.