Issue 6552 - call setdefault() on correct dictionary

chainedconfigparser.py

 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 import os
 import io
 import ConfigParser
 from StringIO import StringIO
 
 
@@ skipping 198 matching lines @@
             if v == 'bool:false':
                 return False
             return v
 
         if self.has_section(section):
             for k, v in self.items(section):
                 parents = k.split('.')
                 tail = parents.pop()
                 current = base
                 for name in parents:
-                    current = base.setdefault(name, {})
+                    current = current.setdefault(name, {})
 
                 if '\n' in v:
                     current[tail] = [parse_value(x) for x in v.splitlines() if x]
                 else:
                     current[tail] = parse_value(v)
 
     def readfp(self, fp, filename=None):
         raise NotImplementedError
 
     def set(self, section, option, value=None):
         raise NotImplementedError
 
     def add_section(self, section):
         raise NotImplementedError
 
     def remove_option(self, section, option):
         raise NotImplementedError
 
     def remove_section(self, section):
         raise NotImplementedError