Scenario:
Create blacklist using string that cannot be used either as a regex or as a zone name, for example: 
patterns = ['', '#(*&^%$%$#@$']


Empty pattern console result:
2021-07-01 10:36:29,649 770881 INFO     [tempest.lib.common.rest_client] Request (BlacklistsAdminTest:test_create_blacklist_invalid_pattern): 201 POST http://10.35.64.8/dns/v2/blacklists 0.216s
2021-07-01 10:36:29,650 770881 DEBUG    [tempest.lib.common.rest_client] Request - Headers: {'Content-Type': 'application/json', 'Accept': 'application/json', 'X-Auth-Token': '<omitted>'}
        Body: {"pattern": "", "description": "tempest-2122752535"}
    Response - Headers: {'date': 'Thu, 01 Jul 2021 07:36:29 GMT', 'server': 'Apache/2.4.41 (Ubuntu)', 'location': 'http://10.35.64.8/dns/v2/blacklists/81759d14-1aa4-4395-b4da-0e9f8e024044', 'content-length': '257', 'x-openstack-request-id': 'req-5bbf9f42-6903-4bbe-b670-92860217864d', 'connection': 'close', 'content-type': 'application/json', 'status': '201', 'content-location': 'http://10.35.64.8/dns/v2/blacklists'}
        Body: b'{"id": "81759d14-1aa4-4395-b4da-0e9f8e024044", "pattern": "", "description": "tempest-2122752535", "created_at": "2021-07-01T07:36:30.000000", "updated_at": null, "links": {"self": "http://10.35.64.8/dns/v2/blacklists/81759d14-1aa4-4395-b4da-0e9f8e024044"}}'
}}}

Invalid string (#(*&^%$%$#@$") console result:
2021-07-01 10:32:32,316 770535 INFO     [tempest.lib.common.rest_client] Request (BlacklistsAdminTest:test_create_blacklist_invalid_pattern): 201 POST http://10.35.64.8/dns/v2/blacklists 0.037s
2021-07-01 10:32:32,317 770535 DEBUG    [tempest.lib.common.rest_client] Request - Headers: {'Content-Type': 'application/json', 'Accept': 'application/json', 'X-Auth-Token': '<omitted>'}
        Body: {"pattern": "#(*&^%$%$#@$", "description": "tempest-374346852"}
    Response - Headers: {'date': 'Thu, 01 Jul 2021 07:32:32 GMT', 'server': 'Apache/2.4.41 (Ubuntu)', 'location': 'http://10.35.64.8/dns/v2/blacklists/4527e92e-f6f9-438a-917b-7478a2c02e0c', 'content-length': '268', 'x-openstack-request-id': 'req-2f6969a4-5cce-417b-80f2-509e42128499', 'connection': 'close', 'content-type': 'application/json', 'status': '201', 'content-location': 'http://10.35.64.8/dns/v2/blacklists'}
        Body: b'{"id": "4527e92e-f6f9-438a-917b-7478a2c02e0c", "pattern": "#(*&^%$%$#@$", "description": "tempest-374346852", "created_at": "2021-07-01T07:32:32.000000", "updated_at": null, "links": {"self": "http://10.35.64.8/dns/v2/blacklists/4527e92e-f6f9-438a-917b-7478a2c02e0c"}}'

Actual Result:
Blacklist is successfully created

Expected result:
400 BadRequest