Attribute Error running PyTest

I am currently trying to run some test on a program, but suddenly I keep getting the same error, no matter what I run it on, be it the program I want to test, a basic tutorial file, an empty file or nothing. The error is :

  File "/usr/local/bin/py.test", line 11, in <module>
    sys.exit(main())
  File "/usr/local/lib/python2.7/dist-packages/_pytest/config.py", line 38, in main
    config = _prepareconfig(args, plugins)
  File "/usr/local/lib/python2.7/dist-packages/_pytest/config.py", line 117, in _prepareconfig
    pluginmanager=pluginmanager, args=args)
  File "/usr/local/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py", line 724, in __call__
    return self._hookexec(self, self._nonwrappers + self._wrappers, kwargs)
  File "/usr/local/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py", line 338, in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
  File "/usr/local/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py", line 333, in <lambda>
    _MultiCall(methods, kwargs, hook.spec_opts).execute()
  File "/usr/local/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py", line 595, in execute
    return _wrapped_call(hook_impl.function(*args), self.execute)
  File "/usr/local/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py", line 249, in _wrapped_call
    wrap_controller.send(call_outcome)
  File "/usr/local/lib/python2.7/dist-packages/_pytest/helpconfig.py", line 28, in pytest_cmdline_parse
    config = outcome.get_result()
  File "/usr/local/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py", line 279, in get_result
    _reraise(*ex)  # noqa
  File "/usr/local/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py", line 264, in __init__
    self.result = func()
  File "/usr/local/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py", line 596, in execute
    res = hook_impl.function(*args)
  File "/usr/local/lib/python2.7/dist-packages/_pytest/config.py", line 852, in pytest_cmdline_parse
    self.parse(args)
  File "/usr/local/lib/python2.7/dist-packages/_pytest/config.py", line 957, in parse
    self._preparse(args)
  File "/usr/local/lib/python2.7/dist-packages/_pytest/config.py", line 918, in _preparse
    self.pluginmanager.load_setuptools_entrypoints("pytest11")
  File "/usr/local/lib/python2.7/dist-packages/_pytest/vendored_packages/pluggy.py", line 501, in load_setuptools_entrypoints
    plugin = ep.load()
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 2088, in load
    entry = __import__(self.module_name, globals(),globals(), ['__name__'])
  File "/usr/local/lib/python2.7/dist-packages/pytest_bdd/__init__.py", line 3, in <module>
    from pytest_bdd.steps import given, when, then
  File "/usr/local/lib/python2.7/dist-packages/pytest_bdd/steps.py", line 43, in <module>
    from .feature import parse_line, force_encode
  File "/usr/local/lib/python2.7/dist-packages/pytest_bdd/feature.py", line 37, in <module>
    from . import exceptions
  File "/usr/local/lib/python2.7/dist-packages/pytest_bdd/exceptions.py", line 65, in <module>
    @six.python_2_unicode_compatible
AttributeError: 'module' object has no attribute 'python_2_unicode_compatible'

I could not find anything relating specifically to this bug in pytest, although it seems to occur in other programs using the six module. I tried reinstalling both six and pytest, but so far no luck. What is the problem and how to solve it?

Here is the result for print(six.__file__, dir(six)):

('/usr/lib/python2.7/dist-packages/six.pyc',
 ['BytesIO', 'Iterator', 'MAXSIZE', 'Module_six_moves_urllib',
  'Module_six_moves_urllib_error', 'Module_six_moves_urllib_parse',
  'Module_six_moves_urllib_request', 'Module_six_moves_urllib_response',
  'Module_six_moves_urllib_robotparser', 'MovedAttribute', 'MovedModule',
  'PY2', 'PY3', 'StringIO', '_LazyDescr', '_LazyModule', '_MovedItems',
  '__author__', '__builtins__', '__doc__', '__file__', '__name__',
  '__package__', '__version__', '_add_doc', '_func_closure', '_func_code',
  '_func_defaults', '_func_globals', '_import_module', '_iteritems',
  '_iterkeys', '_iterlists', '_itervalues', '_meth_func', '_meth_self',
  '_moved_attributes', '_urllib_error_moved_attributes',
  '_urllib_parse_moved_attributes', '_urllib_request_moved_attributes',
  '_urllib_response_moved_attributes', '_urllib_robotparser_moved_attributes',
  'add_metaclass', 'add_move', 'advance_iterator', 'b', 'binary_type',
  'byte2int', 'callable', 'class_types', 'create_bound_method', 'exec_',
  'get_function_closure', 'get_function_code', 'get_function_defaults',
  'get_function_globals', 'get_method_function', 'get_method_self',
  'get_unbound_function', 'indexbytes', 'int2byte', 'integer_types',
  'iterbytes', 'iteritems', 'iterkeys', 'iterlists', 'itervalues', 'moves',
  'next', 'operator', 'print_', 'remove_move', 'reraise', 'string_types',
  'sys', 'text_type', 'types', 'u', 'unichr', 'with_metaclass'])