When I look at oauth2client's coveralls setup, I see "cover" as its own tox environment. Why is that not the right thing to do here?

We will probably want to fix that in oauth2client. Right now, it only checks the coverage in 2.7. The way it is implemented there, the nose tests are ran normally first, then in 2.7, the nose tests are ran again with the coverage check; so the test are running twice when only once is needed (per version).

I don't see a reason to not check the coverage for all versions when the tests are ran the first time, since some of the code only runs in 2.x and others only in 3.x. Coveralls will also give you a summary for all of the test environments afterwards.

Ok, I cleaned up the tox config file a lot and updated the PR.

Split the commit into 2, how's it look now?

Looks much better; thanks!