TST: skip: Quiet Runner-based dependency checks

[kyleam]

The point is to check whether the functionality is available, so don't pollute the test output with alarming things like

[ERROR  ] stderr| Error: communication error [..]
[ERROR  ] Failed to run ['condor_status'] under None. [...]

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This is just a minor cosmetic thing that was bothering me as I was working on another topic.

[codecov[bot]]

Codecov Report

Merging #510 into master will decrease coverage by 0.00%. The diff coverage is 75.00%.

@@            Coverage Diff             @@
##           master     #510      +/-   ##
==========================================
- Coverage   89.60%   89.60%   -0.01%     
==========================================
  Files         148      148              
  Lines       12281    12290       +9     
==========================================
+ Hits        11005    11013       +8     
- Misses       1276     1277       +1     

Impacted Files	Coverage Δ
reproman/tests/skip.py	97.75% <66.66%> (ø)
reproman/support/external_versions.py	86.46% <69.23%> (-0.15%)	:arrow_down:
reproman/cmd.py	78.66% <100.00%> (+0.43%)	:arrow_up:

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[kyleam]

I've updated the series to avoid a few other spots where .run() failures were presented as errors despite being expected. If there is worry about creating conflicts with external_versions.py or cmd.py updates that could come in via the branch 3rd, I'm okay dropping all of the commits after the second.

[yarikoptic]

As for the 3rd... I think they so would be manageable, and I didn't check how much we already diverged, may be we would just pick up needed fixes as we go