force recent isort

Author: jschlyter

.travis.yml

@@ -13,7 +13,7 @@ install:
   - pip install codecov
   - pip install tox
   - pip install tox-travis
-  - pip install isort
+  - pip install "isort>=5.0.2"
   - pip install black
 script:
   - isort --check --recursive src tests