Fix code style

Author: goanpeca

colosseum/declaration.py

@@ -623,8 +623,10 @@ def __str__(self):
         non_default = []
         for name in _CSS_PROPERTIES:
             try:
-                getattr(self, '_%s' % name)
-                non_default.append((name.replace('_', '-'), getattr(self, name)))
+                non_default.append((
+                    name.replace('_', '-'),
+                    getattr(self, '_%s' % name)
+                ))
             except AttributeError:
                 pass