I discovered another issue while deploying to PythonAnywhere (maybe it’s applicable to other PAAS providers as well).

There was an odd ImportError when running manage.py. In the specific case I had, it showed up when running the tests with coverage: from Unipath import Path ImportError: No module named ‘Unipath’. It turned out I hadn’t installed coverage in the virtual environment, which meant the system was using the default one. Installing coverage in the virtual environment as well fixed the problem.