Problems with the test suite

[Jesse Gibbons]

I'm still working on making 43193 ready to apply. I added a test, and it 
looks like my to the build script --with-source option broke something. 
I am getting error messages, but I don't know where in the code they are 
occurring. Is there any way I can get a stack trace when errors are 
raised during tests? I also noticed nearly all of the tests assert 
multiple things simultaneously, compounded by the `and` function. When 
one of those things is found to be false, the test fails, but I don't 
know which part of the assertion is false.

Are there any advantages to using Guix's custom testing API over other 
testing APIs like SRFI-64? If not, why not transition the test suite to 
use one of them?

-Jesse