Bump pytest from 5.4.3 to 6.1.0 (#540)

Bumps [pytest](https://github.com/pytest-dev/pytest) from 5.4.3 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@5.4.3...6.1.0)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

dev-requirements.txt

@@ -3,7 +3,7 @@
 blinker==1.4
 coverage==5.2.1
 mock==2.0.0; python_version == "2.7"
-pytest==5.4.3; python_version > "2.7"
+pytest==6.1.0; python_version > "2.7"
 pytest<5.0; python_version == "2.7"
 pycodestyle==2.6.0
 pyflakes==2.2.0