After looking at older documentation of flake8, I think all flake8 3.…

…* version should work: http://flake8.pycqa.org/en/3.0.0/user/python-api.html. So removing the version check completly.

setup.py

@@ -101,7 +101,7 @@ def do_setup():
           install_requires=['numpy>=1.9.1', 'scipy>=0.14', 'six>=1.9.0'],
           # pygments is a dependency for Sphinx code highlight
           extras_require={
-              'test': ['nose>=1.3.0', 'parameterized', 'flake8<3,>3.3'],
+              'test': ['nose>=1.3.0', 'parameterized', 'flake8'],
               'doc': ['Sphinx>=0.5.1', 'pygments']
           },
           package_data={