Ensure we're only on Python 2.7

As FichteFoll pointed out on IRC, this line could include Python 3s
less than 3.2 as well.

src/flake8/utils.py

@@ -173,7 +173,7 @@ def can_run_multiprocessing_on_windows():
     :rtype:
         bool
     """
-    is_new_enough_python27 = sys.version_info >= (2, 7, 11)
+    is_new_enough_python27 = (2, 7, 11) <= sys.version_info < (3, 0)
     is_new_enough_python3 = sys.version_info > (3, 2)
     return is_new_enough_python27 or is_new_enough_python3