Bump isort from 4.3.21 to 5.7.0

Bumps [isort](https://github.com/pycqa/isort) from 4.3.21 to 5.7.0.
- [Release notes](https://github.com/pycqa/isort/releases)
- [Changelog](https://github.com/PyCQA/isort/blob/develop/CHANGELOG.md)
- [Commits](PyCQA/isort@4.3.21...5.7.0)

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

requirements.txt

@@ -20,9 +20,14 @@ flake8==3.8.4
     # via
     #   -r requirements.in
     #   flake8-isort
+importlib-metadata==3.7.3
+    # via
+    #   flake8
+    #   pluggy
+    #   pytest
 iniconfig==1.1.1
     # via pytest
-isort==4.3.21
+isort==5.7.0
     # via flake8-isort
 mccabe==0.6.1
     # via flake8
@@ -66,6 +71,10 @@ testfixtures==6.14.0
     # via flake8-isort
 toml==0.10.2
     # via pytest
+typing-extensions==3.7.4.3
+    # via importlib-metadata
+zipp==3.4.1
+    # via importlib-metadata
 
 # The following packages are considered to be unsafe in a requirements file:
 # pip