Bump pytest from 5.3.5 to 5.4.1

Bumps [pytest](https://github.com/pytest-dev/pytest) from 5.3.5 to 5.4.1.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/pytest-dev/pytest/compare/5.3.5...5.4.1)

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

requirements-dev.txt

@@ -1,7 +1,7 @@
 -e .
 flake8==3.7.9
 async-timeout==3.0.1
-pytest==5.3.5
+pytest==5.4.1
 pytest-cov==2.8.1
 pytest-mock==2.0.0
 coverage==5.0.3