fix_UserDict: TypeError: 'Leaf' object is not subscriptable

[jayvdb]

Futurizing https://github.com/weijia/iconizer

> futurize -wn -f libfuturize.fixes.fix_UserDict iconizer/msg_service/msg_def/cmd_msg_base.py
Traceback (most recent call last):
  File "/usr/bin/futurize", line 11, in <module>
    load_entry_point('future==0.18.2', 'console_scripts', 'futurize')()
  File "/usr/lib/python3.8/site-packages/libfuturize/main.py", line 312, in main
    rt.refactor(args, options.write, None,
  File "/usr/lib64/python3.8/lib2to3/refactor.py", line 686, in refactor
    return super(MultiprocessRefactoringTool, self).refactor(
  File "/usr/lib64/python3.8/lib2to3/refactor.py", line 282, in refactor
    self.refactor_file(dir_or_file, write, doctests_only)
  File "/usr/lib64/python3.8/lib2to3/refactor.py", line 727, in refactor_file
    return super(MultiprocessRefactoringTool, self).refactor_file(
  File "/usr/lib64/python3.8/lib2to3/refactor.py", line 335, in refactor_file
    tree = self.refactor_string(input, filename)
  File "/usr/lib64/python3.8/lib2to3/refactor.py", line 367, in refactor_string
    self.refactor_tree(tree, name)
  File "/usr/lib64/python3.8/lib2to3/refactor.py", line 441, in refactor_tree
    new = fixer.transform(node, results)
  File "/usr/lib/python3.8/site-packages/libfuturize/fixes/fix_UserDict.py", line 99, in transform
    bare_name = results["bare_with_attr"][0]
TypeError: 'Leaf' object is not subscriptable