(Original issue 13 created by yeputons on 2019-03-03T06:40:36.920416+00:00)
Example error:
pluggy.manager.PluginValidationError: unknown hook 'pytest_namespace' in plugin <module 'pytest_quickcheck.plugin' from '/usr/local/lib/python3.6/dist-packages/pytest_quickcheck/plugin.py'>
It's due to the using of deprecated pytest_namespace hook (since 3.7.0) which was removed in PyTest 4.1.0.
There is a guide on updating