In the Openstack Identity API v3.9 there was introduced the new "tags" field in the Project resource.
It seems Openstack4j is not compatible with it, causing the following JsonMappingException:
javax.ws.rs.ProcessingException: com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.lang.String out of START_ARRAY token
at [Source: java.io.ByteArrayInputStream@413ecd76; line: 1, column: 179] (through reference chain: org.openstack4j.openstack.identity.v3.domain.KeystoneProject["tags"])