Fix uninitialized auth_data when providing token via env

    def __init__(self, username='', password='', block_size=None, cache_type="bytes", cache_options=None, asynchronous=False, loop=None, **storage_options):

        self.kwargs = storage_options

        self.auth_data = {}

        def deny(*args, **kwargs):

            raise OSError(errno.EROFS)