Create server volume fails due to TypeError

We started seeing the following error in heat which uses this client API.
I suspect that the issue is caused by API microversion 1.101 .
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Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource Traceback (most recent call last):
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource File "/opt/stack/heat/heat/engine/resource.py", line 902, in _action_recorder
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource yield
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource File "/opt/stack/heat/heat/engine/resource.py", line 1014, in _do_action
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource yield from self.action_handler_task(action, args=handler_args)
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource File "/opt/stack/heat/heat/engine/resource.py", line 956, in action_handler_task
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource handler_data = handler(*args)
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource ^^^^^^^^^^^^^^
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource File "/opt/stack/heat/heat/engine/resources/volume_base.py", line 194, in handle_create
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource attach_id = self.client_plugin('nova').attach_volume(
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource File "/opt/stack/heat/heat/engine/clients/os/nova.py", line 686, in attach_volume
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource va = self.client().volumes.create_server_volume(
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource File "/opt/stack/data/venv/lib/python3.12/site-packages/novaclient/api_versions.py", line 393, in substitution
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource return methods[-1].func(obj, *args, **kwargs)
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource File "/opt/stack/data/venv/lib/python3.12/site-packages/novaclient/v2/volumes.py", line 103, in create_server_volume
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource return self._create(
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource ^^^^^^^^^^^^^
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource File "/opt/stack/data/venv/lib/python3.12/site-packages/novaclient/base.py", line 372, in _create
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource return obj_class(self, body[response_key], resp=resp)
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource ~~~~^^^^^^^^^^^^^^
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource TypeError: 'NoneType' object is not subscriptable
Feb 27 15:06:51.388724 np404463a926d74 heat-engine[92385]: 2026-02-27 15:06:51.383 92385 TRACE heat.engine.resource
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