capybara/virtualenv/lib/python2.7/site-packages/pip/_vendor/pkg_resources/__init__.py
def _markerlib_evaluate(cls, text):
        """
        Evaluate a PEP 426 environment marker using markerlib.
        Return a boolean indicating the marker result in this environment.
        Raise SyntaxError if marker is invalid.
        """
        from pip._vendor import _markerlib
        # markerlib implements Metadata 1.2 (PEP 345) environment markers.
        # Translate the variables to Metadata 2.0 (PEP 426).
        env = _markerlib.default_environment()
        for key in env.keys():
            new_key = key.replace('.', '_')
            env[new_key] = env.pop(key)
        try:
            result = _markerlib.interpret(text, env)
        except NameError as e:
            raise SyntaxError(e.args[0])
        return result
def _markerlib_evaluate(cls, text):
        """
        Evaluate a PEP 426 environment marker using markerlib.
        Return a boolean indicating the marker result in this environment.
        Raise SyntaxError if marker is invalid.
        """
        from pip._vendor import _markerlib
        # markerlib implements Metadata 1.2 (PEP 345) environment markers.
        # Translate the variables to Metadata 2.0 (PEP 426).
        env = _markerlib.default_environment()
        for key in env.keys():
            new_key = key.replace('.', '_')
            env[new_key] = env.pop(key)
        try:
            result = _markerlib.interpret(text, env)
        except NameError as e:
            raise SyntaxError(e.args[0])
        return result
Evaluate a PEP 426 environment marker using markerlib.
        Return a boolean indicating the marker result in this environment.
        Raise SyntaxError if marker is invalid.