Bump psutil from 4.4.2 to 5.6.6

Bumps [psutil](https://github.com/giampaolo/psutil) from 4.4.2 to 5.6.6.
- [Release notes](https://github.com/giampaolo/psutil/releases)
- [Changelog](https://github.com/giampaolo/psutil/blob/master/HISTORY.rst)
- [Commits](giampaolo/psutil@release-4.4.2...release-5.6.6)

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

requirements.txt

@@ -2,6 +2,6 @@ pytest==5.2.2
 pytest-cov==2.5.1
 requests==2.20.0
 what==0.5.0
-psutil==4.4.2
+psutil==5.6.6
 flake8==3.5.0
 mypy==0.570