-r requirements.txt
flake8==3.6.0
pytest==3.10.1
pytest-cov==2.6.0

-r requirements.txt
flake8==3.6.0
pytest==4.0.0
pytest-cov==2.6.0

Update pytest from 3.10.1 to 4.0.0
Update pytest from 3.10.1 to 4.0.0