Gatling test "error parsing integer value '': Expected option value to be integer, got ''"

Test case:

Traceback (most recent call last):
  File "/root/openattic/gatling/rbd/scenarios.py", line 31, in setUpClass
    cls.replicated_pool_1 = cls.create_test_pool('gatling_pool_replicated_1', 'replicated')
  File "/root/openattic/gatling/rbd/scenarios.py", line 64, in create_test_pool
    res = cls.send_ceph_request('POST', cls.fsid, 'pools', data=pool_data)
  File "/root/openattic/gatling/testcase.py", line 376, in send_ceph_request
    res = cls._do_request(method, url, headers, data=data)
  File "/root/openattic/gatling/testcase.py", line 344, in _do_request
    request=e.request)
requests.exceptions.HTTPError: 500 Server Error: INTERNAL SERVER ERROR for url: http://<oa-host>/openattic/api/ceph/cacd76fb-0972-37cc-bfca-092c921f19b9/pools content: {"detail": "Executing \"osd pool set var=size pool=gatling_pool_replicated_1 val=1\" failed: \"error parsing integer value '': Expected option value to be integer, got ''\" code=EINVAL"}
		

2019-03-08 13:17:29,479 2995 mod_wsgi INFO root#get_django_app_modules - Loaded restapi modules: ifconfig.restapi, userprefs.restapi, cmdlog.restapi, rest.restapi, ceph.restapi, ceph_deployment.restapi, taskqueue.restapi
2019-03-08 13:17:30,534 2985 mod_wsgi INFO root#get_django_app_modules - Loaded restapi modules: ifconfig.restapi, userprefs.restapi, cmdlog.restapi, rest.restapi, ceph.restapi, ceph_deployment.restapi, taskqueue.restapi
2019-03-08 13:17:30,705 2983 mod_wsgi WARNING rest.restapi#gen_new_token - User action canceled: user 'openattic' tried to refresh the authentication token of user 'gatling_testuser'.
2019-03-08 13:17:31,078 2993 mod_wsgi INFO root#get_django_app_modules - Loaded restapi modules: ifconfig.restapi, userprefs.restapi, cmdlog.restapi, rest.restapi, ceph.restapi, ceph_deployment.restapi, taskqueue.restapi
2019-03-08 13:17:34,371 2982 mod_wsgi INFO deepsea#_login - Salt API login successful
2019-03-08 13:17:35,925 2982 mod_wsgi INFO ceph_radosgw.rgw_client#_load_settings - Using DeepSea RGW settings to connect to RGW REST API
2019-03-08 13:17:35,925 2982 mod_wsgi INFO ceph_radosgw.rgw_client#_load_settings - Creating new connection for user: admin
2019-03-08 13:17:36,036 2984 mod_wsgi INFO deepsea#_login - Salt API login successful
2019-03-08 13:17:37,524 2984 mod_wsgi INFO ceph_radosgw.rgw_client#_load_settings - Using DeepSea RGW settings to connect to RGW REST API
2019-03-08 13:17:37,525 2984 mod_wsgi INFO ceph_radosgw.rgw_client#_load_settings - Creating new connection for user: admin
2019-03-08 13:17:38,754 2999 mod_wsgi ERROR utilities#run - Exception when running a librados process.
Traceback (most recent call last):
  File "/srv/openattic/backend/utilities.py", line 152, in run
    self.com_pipe.send(func())
  File "/srv/openattic/backend/ceph/librados.py", line 436, in with_client
    return method(client)
  File "/srv/openattic/backend/ceph/librados.py", line 1058, in <lambda>
    lambda client: client.mon_command(cmd, argdict, output_format), cmd,
  File "/srv/openattic/backend/ceph/librados.py", line 387, in mon_command
    {'prefix': cmd}, argdict, output_format, default_return, target)
  File "/srv/openattic/backend/ceph/librados.py", line 410, in mon_command
    raise ExternalCommandError(err, cmd, argdict, code=ret)
ExternalCommandError: Executing "osd pool set var=min_size pool=gatling_pool_replicated_1 val=1" failed: "error parsing integer value '': Expected option value to be integer, got ''" code=EINVAL
2019-03-08 13:17:38,758 2999 mod_wsgi ERROR ceph.librados#undo_transaction - Will now undo steps performed.
Traceback (most recent call last):
  File "/srv/openattic/backend/ceph/librados.py", line 490, in undo_transaction
    yield undo_context
  File "/srv/openattic/backend/ceph/models.py", line 510, in save
    key))
  File "/srv/openattic/backend/ceph/librados.py", line 461, in wrapper
    ret = next(runner)
  File "/srv/openattic/backend/ceph/librados.py", line 673, in osd_pool_set
    output_format='string')
  File "/srv/openattic/backend/ceph/librados.py", line 1059, in _call_mon_command
    timeout)
  File "/srv/openattic/backend/ceph/librados.py", line 439, in call_librados
    return run_in_external_process(with_client, cmd_name, timeout)
  File "/srv/openattic/backend/utilities.py", line 165, in run_in_external_process
    raise res
ExternalCommandError: Executing "osd pool set var=min_size pool=gatling_pool_replicated_1 val=1" failed: "error parsing integer value '': Expected option value to be integer, got ''" code=EINVAL
2019-03-08 13:17:38,789 2999 mod_wsgi INFO ceph.librados#impl - Executing fallback for mon_allow_pool_delete=false
Executing "osd pool delete pool2=gatling_pool_replicated_1 sure=--yes-i-really-really-mean-it pool=gatling_pool_replicated_1" failed: "pool deletion is disabled; you must first set the mon_allow_pool_delete config option to true before you can destroy a pool" code=EPERM
2019-03-08 13:17:39,800 2999 mod_wsgi ERROR exception#custom_handler - Internal Server Error: None
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/rest_framework/views.py", line 400, in dispatch
    response = handler(request, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/rest_framework/mixins.py", line 54, in create
    self.object = serializer.save(force_insert=True)
  File "/usr/lib/python2.7/site-packages/rest_framework/serializers.py", line 599, in save
    self.save_object(self.object, **kwargs)
  File "/usr/lib/python2.7/site-packages/rest_framework/serializers.py", line 1041, in save_object
    obj.save(**kwargs)
  File "/srv/openattic/backend/ceph/models.py", line 510, in save
    key))
  File "/srv/openattic/backend/ceph/librados.py", line 461, in wrapper
    ret = next(runner)
  File "/srv/openattic/backend/ceph/librados.py", line 673, in osd_pool_set
    output_format='string')
  File "/srv/openattic/backend/ceph/librados.py", line 1059, in _call_mon_command
    timeout)
  File "/srv/openattic/backend/ceph/librados.py", line 439, in call_librados
    return run_in_external_process(with_client, cmd_name, timeout)
  File "/srv/openattic/backend/utilities.py", line 165, in run_in_external_process
    raise res
ExternalCommandError: Executing "osd pool set var=min_size pool=gatling_pool_replicated_1 val=1" failed: "error parsing integer value '': Expected option value to be integer, got ''" code=EINVAL
2019-03-08 13:17:42,604 2792 runsystemd INFO taskqueue.models#transition - Task Transition: Not Started -> Running
2019-03-08 13:17:42,610 2792 runsystemd INFO taskqueue.models#run_once - Running 1: ceph.tasks.track_pg_creation with [u'e991c0ed-b3a8-35e5-a111-5963b4c05563', 8, 0, 1], {}. Estimated: None
2019-03-08 13:17:42,652 2792 runsystemd ERROR taskqueue.models#run_once - Failed to run "ceph.tasks.track_pg_creation with [u'e991c0ed-b3a8-35e5-a111-5963b4c05563', 8, 0, 1], {}" created "2019-03-08 13:17:38.716317"
Traceback (most recent call last):
  File "/srv/openattic/backend/taskqueue/models.py", line 79, in run_once
    res = task.run_once()
  File "/srv/openattic/backend/taskqueue/models.py", line 254, in run_once
    res = self.wrapper.call_now(*self.args, **self.kwargs)
  File "/srv/openattic/backend/taskqueue/models.py", line 335, in call_now
    return self._orig_func(*args, **kwargs)
  File "/srv/openattic/backend/ceph/tasks.py", line 84, in track_pg_creation
    pool = CephPool.objects.get(id=pool_id)
  File "/usr/lib/python2.7/site-packages/django/db/models/manager.py", line 151, in get
    return self.get_queryset().get(*args, **kwargs)
  File "/srv/openattic/backend/nodb/models.py", line 216, in get
    filtered_data.query))
DoesNotExist: CephPool matching query "<NoDbQuery q=(AND: ('id', 8)), ordering=[]>" does not exist.
2019-03-08 13:17:42,670 2792 runsystemd INFO taskqueue.models#finish_task - Task finished: CephPool matching query "<NoDbQuery q=(AND: ('id', 8)), ordering=[]>" does not exist.
2019-03-08 13:17:42,670 2792 runsystemd INFO taskqueue.models#transition - Task Transition: Running -> Exception