* Improve support using external modules with zsh
Spack integrates with external modules by launching a python subprocess
to scrape the path from the module command. In zsh, subshells do not
inheret functions defined in the parent shell (only environment
variables). This breaks the module function in module_cmd.py.
As a workaround, source the module commands using $MODULESHOME prior to
running the module command.
* Fix formatting
* Fix flake error
* Add guard around sourcing module file
* Add improved unit testing to module src command
* Correct style
* Another attempt at style
* formatting again
* formatting again
---------
Co-authored-by: psakievich <psakiev@sandia.gov>
335fca7049