raise exception in case there is already taken host in infoblox

gso/services/infoblox.py

@@ -250,9 +250,8 @@ def create_host_by_ip(
                         :term:`GSO`.
     """
     if not hostname_available(hostname):
-        msg = f"FQDN {hostname} already taken, nothing to be done."
-        logger.warning(msg)
-        return
+        msg = f"FQDN '{hostname}' is already in use, allocation aborted."
+        raise AllocationError(msg)
 
     conn, oss = _setup_connection()
     ipv6_object = objects.IP.create(ip=str(ipv6_address), mac=NULL_MAC, configure_for_dhcp=False)