[bug#27599] [PATCH 1/2] gnu: Add cmdtest.

[Arun Isaac <arunisaac@systemreboot.net>]

> I can't figure out what's going wrong with the test suite. Perhaps
> someone familiar with the Coverage Test Runner module in python can be
> of assistance.

I made some progress. Here are the arguments I used.

(arguments
 `(#:python ,python-2
   #:phases
   (modify-phases %standard-phases
     ;; check phase needs to be run before the build phase. If not, the
     ;; coverage test runner looks for tests for the built source files,
     ;; and fails.
     (delete 'check)
     (add-before 'build 'check
       (lambda _
         (substitute* "yarn"
           (("/bin/sh") (which "sh")))
         (zero? (system* "python" "setup.py" "check")))))))

However, there is still one (hopefully) last test that is failing. This
happens when `python setup.py check' runs `./cmdtest yarn.tests'. I'm
not able to figure out exactly what the issue is. But, I noticed that
this test fails only in the build environment, and runs fine in my user
environment. So, this must be due to something that is missing in the
build environment -- possibly some environment variable. Check it out
and let me know. I will also continue trying.