CI: Have codecov collect on all platforms

[aragilar]

This adds enforcement of codecov success (which if it's a problem I'll drop, but hopefully not), and combines the coverage explicitly (so hopefully codecov will just work on all platforms now...).

Closes #1358 (now).

[codecov]

Codecov Report

Merging #1381 into master will increase coverage by 0.29%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1381      +/-   ##
==========================================
+ Coverage   84.28%   84.57%   +0.29%     
==========================================
  Files          17       17              
  Lines        2049     2049              
==========================================
+ Hits         1727     1733       +6     
+ Misses        322      316       -6

Impacted Files	Coverage Δ
h5py/_hl/dataset.py	87.91% <0%> (+0.21%)	⬆️
h5py/_hl/compat.py	83.33% <0%> (+27.77%)	⬆️

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[aragilar]

Assuming this passes on all systems, this should be ready to merge. Closes #1358. This also fixes appveyor, so our overall overage should go up (given we should have coverage on Windows systems).

[takluyver]

Is it feasible to just call coverage combine ... from the CI configuration before invoking codecov, rather than maintaining our own wrapper script to upload coverage?

[takluyver]

Also, while we're looking at coverage stuff: would you be OK with setting a threshold, e.g. 0.5%, in codecov config? If I understand correctly, this would let coverage drop by that much without giving the PR a red cross. It's been annoying me that even tiny coverage drops (e.g. from removing some tested code) make it look like CI has failed.

[aragilar]

Codecov seems to have real issues finding the files on Windows (which is why I wrote that script in python to be cross platform), which is why I wrote that script. I suspect there's some issue with how the python codecov script handles file paths internally, and given we'd need to wait for any patch to be merged (there's still a patch for collecting data on azure waiting to be merged on their system - codecov/codecov-python#194), I'd rather keep the script until codecov properly supports azure with windows. I did think about moving to coveralls (in the hope of having something "just work") but it looks like their azure support is no better (and their python support worse)...

I'll add the codecov.yml increasing the threshold, it annoys me also.

[takluyver]

OK, fair enough. Is it possible that we're waiting for a fix I already got merged there to be released? codecov/codecov-python#202

[aragilar]

Yeah, it looks like we're waiting on your fix to codecov (I notice the coverage upload worked this time, even though the changes should have made no difference...).