Merge pull request #88 from andrivet/pyup-update-isort-4.3.21-to-5.1.1

Update isort to 5.1.1

Author: andrivet

requirements-dev.txt

@@ -2,7 +2,7 @@
 pytest==5.4.3
 tox==3.17.1
 flake8==3.8.3
-isort==4.3.21
+isort==5.1.1
 docutils==0.16
 check-manifest==0.42
 readme-renderer==26.0