Enable flake8 and fix errors

Author: garyp

sifter/grammar/comparator.py

@@ -1,3 +1,5 @@
+import re
+
 import sifter.comparator
 
 __all__ = ('Comparator',)

sifter/tests/size.py

@@ -26,7 +26,7 @@ def __init__(self, arguments=None, tests=None):
                 }
             )
         self.validate_tests_size(0)
-        self.comparison_fn = COMPARISON_FNS[tagged_args['size'][0]]
+        self.comparison_fn = self.COMPARISON_FNS[tagged_args['size'][0]]
         self.comparison_size = tagged_args['size'][1]
 
     def evaluate(self, message, state):

tox.ini

@@ -7,7 +7,19 @@
 envlist = py27
 
 [testenv]
-deps = 
+deps = flake8
 
 commands =
+    # stop the build if there are Python syntax errors or undefined names
+    flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
+    # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
+    flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
+
     python -m unittest discover -v
+
+[flake8]
+exclude =
+    # this is the default list of excludes
+    .svn,CVS,.bzr,.hg,.git,__pycache__,.tox,.eggs,*.egg,
+    # auto-generated files
+    parsetab.py