Raise a SaltInvocationError if invalid_kwargs is non-empty

def invalid_kwargs(invalid_kwargs, raise_exc=True):
    '''
    Raise a SaltInvocationError if invalid_kwargs is non-empty
    '''
    if invalid_kwargs:
        if isinstance(invalid_kwargs, dict):
            new_invalid = [
                '{0}={1}'.format(x, y)
                for x, y in six.iteritems(invalid_kwargs)
            ]
            invalid_kwargs = new_invalid
    msg = (
        'The following keyword arguments are not valid: {0}'
        .format(', '.join(invalid_kwargs))
    )
    if raise_exc:
        raise SaltInvocationError(msg)
    else:
        return msg