Ryan, what are the exact steps to reproduce the problem? This is what I get when I run the code you included:

>>> import argparse
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('things', nargs=argparse.REMAINDER, default=['nothing'])
_StoreAction(option_strings=[], dest='things', nargs='...', const=None, default=['nothing'], type=None, choices=None, help=None, metavar=None)
>>> parser.parse_args([])
Namespace(things=[])
>>> Namespace(things=[])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'Namespace' is not defined