fix flake8 errors

dataset/freeze/config.py

@@ -63,7 +63,7 @@ class Export(object):
 
     def get_normalized(self, name, default=None):
         value = self.get(name, default=default)
-        if not value in [None, default]:
+        if value not in [None, default]:
             value = str(value).lower().strip()
         return value
 

dataset/freeze/format/fcsv.py

@@ -21,7 +21,7 @@ class CSVSerializer(Serializer):
 
     def write(self, path, result):
         keys = list(result.keys())
-        if not path in self.handles:
+        if path not in self.handles:
             fh = open(path, 'wb')
             writer = csv.writer(fh)
             writer.writerow([k.encode('utf-8') for k in keys])

dataset/util.py

@@ -1,4 +1,4 @@
-#coding: utf-8
+# coding: utf-8
 import re
 
 SLUG_REMOVE = re.compile(r'[,\s\.\(\)/\\;:]*')