Bump pytest from 4.4.0 to 6.1.0

Bumps [pytest](https://github.com/pytest-dev/pytest) from 4.4.0 to 6.1.0.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@4.4.0...6.1.0)

Signed-off-by: dependabot[bot] <support@github.com>

requirements-dev.txt

@@ -1,7 +1,7 @@
 -r requirements.txt
 
 coverage==4.5.3
-pytest==4.4.0
+pytest==6.1.0
 pytest-cov==2.6.1
 responses==0.10.6
 coveralls==1.7.0