DeprecationWarning durnig pytest-cov

[Jakub89]

We've updated nameko from stable to 3.0.0rc8 to get rid of pytest warnings. And we were successful, but one different warning appear:

========================================== warnings summary ==========================================
.../lib/python3.8/site-packages/nameko/messaging.py:38
  .../lib/python3.8/site-packages/nameko/messaging.py:38: DeprecationWarning: invalid escape sequence \.
    re.sub("^{}\.".format(prefix), "", key): value

-- Docs: https://docs.pytest.org/en/latest/warnings.html

Environment:

• Nameko version: 3.0.0rc8
• Python version: 3.8.2
• OS: Manjaro Linux 64-bit GNOME 3.36.2
• pytest: 5.4.1
• pytest-cov: 2.8.1

[zsiciarz]

Looks like the regex string is missing r prefix. I proposed a fix in #690 .

[mattbennett]

Fixed in #690. Thanks @zsiciarz!