New flake8

.travis.yml

@@ -36,7 +36,7 @@ install:
   - pip install pip==20.2.1
   - pip install setuptools
   - pip install wheel==0.29.0
-  - pip install --upgrade -I flake8==3.9.2
+  - pip install --upgrade -I flake8==5.0.4
   - pip install -e .[test] --trusted-host github.com
 before_script:
   - flake8 .