Allow to upload and test specific versions
Currently, you cannot test releases other than the most recent one.
Example: I've just uploaded version 0.3.2 via devpi. Now I want to backport some of the changes to an older but still to be maintained version 0.2.8.
devpi upload && devpi test my-package
will not work in this instance because that will test version 0.3.2!
I would need something like
devpi test my-package==0.2.8