Try to fix/improve reporting of test_request_garbage

[nicoddemus]

• Run it in a subprocess to reduce possible intereference from the outer pytest
• Print the leaked objects to see if they provide any hints

[codecov]

Codecov Report

Merging #4457 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #4457      +/-   ##
==========================================
+ Coverage    95.9%   95.91%   +<.01%     
==========================================
  Files         111      111              
  Lines       25085    25085              
  Branches     2447     2447              
==========================================
+ Hits        24059    24061       +2     
+ Misses        724      723       -1     
+ Partials      302      301       -1

Flag	Coverage Δ
#docs	30.09% <ø> (+0.07%)	⬆️
#doctesting	30.09% <ø> (+0.07%)	⬆️
#linting	30.09% <ø> (+0.07%)	⬆️
#linux	95.73% <100%> (-0.01%)	⬇️
#nobyte	92.67% <0%> (ø)	⬆️
#numpy	93.45% <0%> (-0.02%)	⬇️
#pexpect	41.87% <ø> (-0.03%)	⬇️
#py27	94.04% <100%> (+0.01%)	⬆️
#py34	92.18% <100%> (+0.06%)	⬆️
#py35	92.2% <100%> (+0.06%)	⬆️
#py36	92.22% <100%> (+0.06%)	⬆️
#py37	94.11% <100%> (ø)	⬆️
#trial	93.45% <0%> (-0.02%)	⬇️
#windows	94.13% <100%> (ø)	⬆️
#xdist	93.98% <0%> (ø)	⬆️

Impacted Files	Coverage Δ
testing/python/fixture.py	99.24% <100%> (ø)	⬆️
src/_pytest/capture.py	93.87% <0%> (+0.45%)	⬆️

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[nicoddemus]

If someone can merge this in the merge-master-into-features branch it would be great, I'm away from my computer the entire day at a conference 😁

[blueyed]

If someone can merge this in the merge-master-into-features branch

Done.