tests: fix assert rewriting in non-test modules like api_base.py pytest rewrites assert statements in tests so it can print details about the values involved when the assert fails. Since pytest 3.0.0, this was no longer the case for files/modules that are not discovered as test modules, i.e. starting with 'test_'. Examples are: api/api_base.py models/common.py base.py fixture.py Commit 790aeeddcab598d2aacbbecf86830b608ca8b32b attempted to fix that problem, but seems incorrect. A trailing dot should not be there.

# requirements.txt file for use as "pip install -r requirements.txt" as a
# readthedocs compatible alternative to "pip install -e ." which is a working
# alternative to "setup.py develop" which doesn't work with Mercurial 3.7
.