Use flake8-import-order for ordering imports

It seems that isort is not compatible with black at the moment:
psf/black#127
PyCQA/isort#694

Both isort and black are working on a solution, but at the moment, we'll use
flake8-import-order instead

.pre-commit-config.yaml

@@ -15,11 +15,11 @@ repos:
     - id: flake8
       language_version: python3.6
 
-  - repo: https://github.com/pre-commit/mirrors-isort
-    rev: v4.3.20
-    hooks:
-      - id: isort
-        language_version: python3.6
+  # - repo: https://github.com/pre-commit/mirrors-isort
+  #   rev: v4.3.20
+  #   hooks:
+  #     - id: isort
+  #       language_version: python3.6
 
   - repo: https://github.com/pre-commit/pre-commit-hooks
     rev: v2.2.3

tox.ini

@@ -32,19 +32,20 @@ skip_install = true
 deps =
     flake8
     flake8-docstrings
+    flake8-import-order>=0.9
     pep8-naming
     flake8-colors
     pylint
     black
-    isort
+    # isort
     bandit
 commands =
     flake8 src/example-package/ tests/ setup.py
     pylint src/example-package --rcfile=tox.ini --disable=similarities
     black -l 100 --check ./
     black -l 100 --diff ./
-    isort --check-only --recursive .
-    isort --diff --recursive .
+    # isort --check-only --recursive .
+    # isort --diff --recursive .
     bandit -r src/example-package
 ignore_errors = true