I'm using tox to run my tests and this is happening on 2.7, 3.4, 3.5 and 3.6.0a0, tox.ini file. To reproduce, run any suite of tests with less than the desired line coverage. Sample traceback

I only noticed this because I'm starting a new project with one test to see if I could get a combined HTML coverage report for all environments.

I'm wondering if this line should be a sys.exit(1) (or similar) instead