Prevent misbehaving dynamic context plugins from ruining coverage

[s0undt3ch]

While working on a dynamic context plugin I encountered an issue where contexts are not unique(I think it's related to subprocess coverage, but I haven't been able to create a small enough example to show here).

While we can argue that the plugin itself should be fixed, this looks like an innocuous change to coveragepy which can prevent these misbehaving plugins from ruining most of the coverage data(not being covered).

[codecov-io]

Codecov Report

Merging #1088 (309f67e) into master (7ff93a9) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1088      +/-   ##
==========================================
- Coverage   91.28%   91.27%   -0.02%     
==========================================
  Files          90       90              
  Lines       13358    13358              
  Branches     1493     1493              
==========================================
- Hits        12194    12192       -2     
- Misses        953      954       +1     
- Partials      211      212       +1     

Impacted Files	Coverage Δ
coverage/sqldata.py	90.77% <ø> (ø)
tests/test_oddball.py	81.54% <0.00%> (-1.20%)	⬇️

[nedbat]

Do you have any more information about what caused the conflict? This is the type of change that can hide useful information about a problem to be fixed. I see that it would be safe to add, but I have qualms.

[s0undt3ch]

Not really, no. The information I currently know is what's mentioned on the description, sub-processes coverage.
What the misbehaving plugin(mine) is doing, can be seen here and here.
Does it help understand the problem?

[ProsperousHeart]

This branch is out of date, and submission is 2+ years ago. Can it be closed?