Check python3

[tetron]

"make release-test" tweaks.

Check that "python" is actually python 3. Also add "pip install -e ." before running tests on HEAD.

[codecov]

Codecov Report

Merging #1478 (6d2ded3) into main (5883109) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1478      +/-   ##
==========================================
+ Coverage   65.74%   65.76%   +0.01%     
==========================================
  Files          89       89              
  Lines       15628    15628              
  Branches     3933     3933              
==========================================
+ Hits        10275    10277       +2     
+ Misses       4262     4260       -2     
  Partials     1091     1091              

Impacted Files	Coverage Δ
cwltool/job.py	77.62% <0.00%> (-0.41%)	⬇️
job.py	62.22% <0.00%> (+0.80%)	⬆️

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[tetron]

I really don't understand why these tests are failing.

[tetron]

Seems like this might be detecting a legitimate bug, but I don't yet know why the test passes in some environments and fails in other environments.

[tetron]

So this is definitely failing due to an underlying bug which is probably the same one described in #1364

The problem is when moving a directory containing a symlink to another file in the temp directory, it doesn't update the symlink to point to the new location.

I don't understand why it is happening on this branch when (a) the changes are so trivial (b) I can't reproduce it except by changing the code to skip a step which mitigates the crash (but not the underlying error).

I either way, I will extend the test to check for expected behavior more thoroughly, and then fix the underlying bug.