flake8/pep8-naming error

$ flake8 cms/translations/xtm/projects_handler.py
Traceback (most recent call last):
  File "/home/emma/Dropbox/eyeo/hg/cms/.tox/py27/bin/flake8", line 10, in <module>
    sys.exit(main())
  File "/home/emma/Dropbox/eyeo/hg/cms/.tox/py27/local/lib/python2.7/site-packages/flake8/main/cli.py", line 18, in main
    app.run(argv)
  File "/home/emma/Dropbox/eyeo/hg/cms/.tox/py27/local/lib/python2.7/site-packages/flake8/main/application.py", line 393, in run
    self._run(argv)
  File "/home/emma/Dropbox/eyeo/hg/cms/.tox/py27/local/lib/python2.7/site-packages/flake8/main/application.py", line 381, in _run
    self.run_checks()
  File "/home/emma/Dropbox/eyeo/hg/cms/.tox/py27/local/lib/python2.7/site-packages/flake8/main/application.py", line 300, in run_checks
    self.file_checker_manager.run()
  File "/home/emma/Dropbox/eyeo/hg/cms/.tox/py27/local/lib/python2.7/site-packages/flake8/checker.py", line 330, in run
    self.run_parallel()
  File "/home/emma/Dropbox/eyeo/hg/cms/.tox/py27/local/lib/python2.7/site-packages/flake8/checker.py", line 294, in run_parallel
    for ret in pool_map:
  File "/usr/lib/python2.7/multiprocessing/pool.py", line 668, in next
    raise value
AttributeError: 'Attribute' object has no attribute 'id'