Install flake8

tests/travis_install.sh

@@ -46,6 +46,7 @@ pip install tox
 pip install codecov
 # use newest pystencils
 pip install git+https://github.com/mabau/pystencils.git
+pip install flake8
 
 if [[ "$COVERAGE" == "true" ]]; then
     pip install -U pytest-cov pytest-virtualenv coverage coveralls flake8