tox.ini contains reference to nonexistent mpicov test environment in its envlist

[joshuavictorchen]

mpicov is provided as an argument to envlist in tox.ini, but is not defined as a test environment. This results in an extraneous run of the default [testenv] commands at the end of the call stack if an empty tox command is executed.

armi/tox.ini

Line 2 in ba08a30

envlist = py38,lint,cov,mpicov

I believe this is an artifact from #521. The mpicov argument was first introduced along with a corresponding [testenv:mpicov] environment definition here:

2c4cc12#diff-ef2cef9f88b4fe09ca3082140e67f5ad34fb65fb6e228f119d3812261ae51449

But it was not updated when that environment definition was changed to [testenv:mpitest] here:

6c35012#diff-ef2cef9f88b4fe09ca3082140e67f5ad34fb65fb6e228f119d3812261ae51449

envlist's mpicov argument should be updated to mpitest to reflect this change, or removed altogether. I suggest the latter, since the mpitest environment only works on POSIX/BASH Linux and would cause the empty tox command to fail for Windows users, if included.

[john-science]

Just to note: mpitest IS used on GitHub:

armi/.github/workflows/unittests.yaml

Line 26 in 498472b

run: tox -e py,mpitest

It is an important test line that we need to preserve.