delete attribute with client error

delete attribute with client error as below:

File "/home/zuul/src/opendev.org/openstack/python-cyborgclient/.tox/py38/lib/python3.8/site-packages/testtools/compat.py", line 26, in reraise
    raise exc_obj.with_traceback(exc_tb)

      File "/home/zuul/src/opendev.org/openstack/python-cyborgclient/.tox/py38/lib/python3.8/site-packages/testtools/matchers/_exception.py", line 97, in match
    result = matchee()

      File "/home/zuul/src/opendev.org/openstack/python-cyborgclient/.tox/py38/lib/python3.8/site-packages/testtools/testcase.py", line 1040, in __call__
    return self._callable_object(*self._args, **self._kwargs)

      File "/home/zuul/src/opendev.org/openstack/python-cyborgclient/cyborgclient/osc/v2/attribute.py", line 136, in take_action
    failures.append(_("Failed to delete attribute \

    KeyError: 'attribute