CustomConfig.py Removed extra characters

I removed these extra characters.

offlineimap/CustomConfig.py

@@ -117,7 +117,7 @@ class CustomConfigParser(SafeConfigParser):
         For instance, for "Account Test", returns "Test"."""
 
         key = key + ' '
-        return [x[len(key):] for x in self.sections() \
+        return [x[len(key):] for x in self.sections()
                 if x.startswith(key)]
 
     def set_if_not_exists(self, section, option, value):
@@ -157,7 +157,7 @@ def CustomConfigDefault():
     pass
 
 
-class ConfigHelperMixin():
+class ConfigHelperMixin:
     """Allow comfortable retrieving of config values pertaining
     to a section.