Figure out how to measure Python test coverage

[edwardhartnett]

Well I used to know how to do this, so I've got to figure it out again. ;-)

[aerorahul]

@edwardhartnett
I have some experience with pytest and coverage in python.
I can write a couple of examples and share, but I am not sure I can take this ON.

[jbathegit]

We should also figure out a way to measure C test coverage. The gcovr utility doesn't currently measure the C portion of the library either; rather, it only does the Fortran portion.

[edwardhartnett]

@jbathegit the spirit is willing, but the flesh is weak. ;-) However gcovr works equally with C code, it just needs to be pointed at the correct subdirectories...

However, if you can figure this out, we will happily use it on the other projects.

[jbathegit]

As of #249, this is now resolved for the C portion of the library.

But we still need to figure out how to measure coverage for the Python portion of the library.