chore(dev_requirements): upgrade flake8 to 3.2.1

See http://flake8.pycqa.org/en/latest/release-notes/index.html

Author: mboersma

Makefile

@@ -60,7 +60,7 @@ test-check:
 	cd rootfs && python manage.py check
 
 test-style:
-	cd rootfs && flake8 --show-pep8 --show-source
+	cd rootfs && flake8 --show-source
 	${SHELLCHECK_PREFIX} $(SHELL_SCRIPTS)
 
 test-unit:

rootfs/dev_requirements.txt

@@ -2,7 +2,7 @@
 coverage==4.2.0
 
 # Run "make flake8" to check python syntax and style
-flake8==2.5.4
+flake8==3.2.1
 
 # code coverage report at https://codecov.io/github/deis/workflow
 codecov==2.0.5