diff --git a/rhodecode/lib/dbmigrate/migrate/versioning/schemadiff.py b/rhodecode/lib/dbmigrate/migrate/versioning/schemadiff.py
--- a/rhodecode/lib/dbmigrate/migrate/versioning/schemadiff.py
+++ b/rhodecode/lib/dbmigrate/migrate/versioning/schemadiff.py
@@ -244,7 +244,7 @@ class SchemaDiff(object):
                 self.tables_different[table_name]=td
 
     def __str__(self):
-        ''' Summarize differences. '''
+        """ Summarize differences. """
         out = []
         column_template ='      %%%is: %%r' % self.label_width