'maas test' fails: ImportError: cannot import name oauth

With maas test command give:

root@maas-serv:~# maas test
Traceback (most recent call last):
  File "/usr/bin/django-admin", line 5, in <module>
    management.execute_from_command_line()
  File "/usr/lib/python2.7/dist-packages/django/core/management/__init__.py", line 429, in execute_from_command_line
    utility.execute()
  File "/usr/lib/python2.7/dist-packages/django/core/management/__init__.py", line 379, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/lib/python2.7/dist-packages/django/core/management/base.py", line 191, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/usr/lib/python2.7/dist-packages/django/core/management/base.py", line 220, in execute
    output = self.handle(*args, **options)
  File "/usr/lib/python2.7/dist-packages/south/management/commands/test.py", line 8, in handle
    super(Command, self).handle(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/django/core/management/commands/test.py", line 37, in handle
    failures = test_runner.run_tests(test_labels)
  File "/usr/lib/python2.7/dist-packages/django/test/simple.py", line 358, in run_tests
    suite = self.build_suite(test_labels, extra_tests)
  File "/usr/lib/python2.7/dist-packages/django/test/simple.py", line 251, in build_suite
    suite.addTest(build_suite(app))
  File "/usr/lib/python2.7/dist-packages/django/test/simple.py", line 77, in build_suite
    test_module = get_tests(app_module)
  File "/usr/lib/python2.7/dist-packages/django/test/simple.py", line 35, in get_tests
    test_module = __import__('.'.join(app_path + [TEST_MODULE]), {}, {}, TEST_MODULE)
  File "/usr/lib/python2.7/dist-packages/piston/tests.py", line 10, in <module>
    from test import TestCase
  File "/usr/lib/python2.7/dist-packages/piston/test.py", line 7, in <module>
    from piston import oauth
ImportError: cannot import name oauth