Fix Pytest4.x compatibility error
Fix Pytest4.x compatibility error

According to pytest docs:

```
[pytest] section in setup.cfg files

Removed in version 4.0.

[pytest] sections in setup.cfg files should now be named [tool:pytest] to
avoid conflicts with other distutils commands.
```

Signed-off-by: Stanislav Levin <d8f28bdabcfedd2870feddb04c5f1bca6a417bec@altlinux.org>

SurveyMonkey/pycobertura,SurveyMonkey/pycobertura