Add test to reproduce non-removed IPC socket file

[Peque]

Fixes #287.

WIP: still only reproducing the error. No fix.

[codecov]

Codecov Report

Merging #293 into master will decrease coverage by 0.13%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #293      +/-   ##
==========================================
- Coverage    99.1%   98.96%   -0.14%     
==========================================
  Files          26       26              
  Lines        3556     3572      +16     
  Branches      258      258              
==========================================
+ Hits         3524     3535      +11     
- Misses         19       22       +3     
- Partials       13       15       +2

Impacted Files	Coverage Δ
osbrain/agent.py	97.71% <100%> (ø)	⬆️
osbrain/tests/test_bugs.py	92.3% <100%> (+8.97%)	⬆️
osbrain/__init__.py	91.66% <0%> (-8.34%)	⬇️
osbrain/tests/test_agent_transport.py	93.97% <0%> (-2.41%)	⬇️

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[Peque]

Closing in favor of #294.