Merge pull request #562 from NeonGraal/pyup-update-pip-21.2-to-21.2.1

Update pip to 21.2.1

requirements_dev.txt

@@ -5,7 +5,7 @@ flake8==3.9.2
 flake8-polyfill==1.0.2
 mypy==0.910
 pathlib2==2.3.6
-pip==21.2
+pip==21.2.1
 pytest==6.2.4
 pytest-runner==5.3.1
 pytest-cov==2.12.1