fix tests with pyzmq 17

[minrk]

libzmq 4.2, which is bundled with pyzmq 17 but can be used with ~any version of pyzmq, does not cleanup ipc files after closing sockets. The fix is to cleanup these files after closing the binding socket.

closes #303

[codecov]

Codecov Report

Merging #305 into master will decrease coverage by 0.66%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #305      +/-   ##
==========================================
- Coverage   99.19%   98.52%   -0.67%     
==========================================
  Files          26       26              
  Lines        3588     3597       +9     
  Branches      257      259       +2     
==========================================
- Hits         3559     3544      -15     
- Misses         16       34      +18     
- Partials       13       19       +6

Impacted Files	Coverage Δ
osbrain/agent.py	98.03% <100%> (-0.11%)	⬇️
osbrain/__init__.py	88.88% <0%> (-11.12%)	⬇️
osbrain/tests/test_helper.py	93.85% <0%> (-6.15%)	⬇️
osbrain/helper.py	94.87% <0%> (-5.13%)	⬇️
osbrain/tests/test_timer.py	96.6% <0%> (-2.43%)	⬇️
osbrain/nameserver.py	97.65% <0%> (-1.57%)	⬇️
osbrain/tests/test_nameserver.py	97.64% <0%> (-0.48%)	⬇️

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[Peque]

Thanks for this PR and for finding the issue with current ZMQ not unlinking those files. It is unfortunate but we definitely need to fix that on our side then.

I will review your changes and fix the remaining issues with CI. You have helped enough already! 😊

[Peque]

Closed in vafour of #307.

@minrk Your commits where squashed but you kept the authorship: afd59ac

Thanks for your help! 😊