pytest plugins

[Ben Woodcroft]

Hi there,

I'm running into clashes when using pytest plugins e.g.

$ ./pre-inst-env guix environment -C --ad-hoc python-pytest-cov
[..]
warning: collision encountered: 
/gnu/store/cfj96msw5ypxcii4z615l03wbjq5hcs9-python-pytest-cov-2.2.0/bin/py.test 
/gnu/store/4hz0mf56b9mm8q97k5iw5xbb909vsz4p-python-pytest-2.7.3/bin/py.test
warning: arbitrarily choosing 
/gnu/store/cfj96msw5ypxcii4z615l03wbjq5hcs9-python-pytest-cov-2.2.0/bin/py.test
[..]

i.e. the pytest executable is included in `python-pytest' as well 
`python-pytest-cov'.

I'm not sure what the best thing to do is here, because no environment 
variable is honoured during the py.test startup sequence when looking 
for plugins:

http://pytest.org/latest/writing_plugins.html#plugin-discovery-order-at-tool-startup

Do any pythonistas have any ideas on how to get around this?

Thanks,
ben