Fix Tricircle Constants module could not be imported

refer to  https://bugs.launchpad.net/tricircle/+bug/1868777

Change-Id: Ifa4fc23527da38e56f0fd8dac23100be29780e33
signed-off-by: zhangchi <zhangchi@szzt.com.cn>
Co-Authored-By: tangzhuo <ztang@hnu.edu.cn>

tricircle/common/request_source.py

@@ -10,9 +10,9 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from neutron_lib import constants as cons
 from oslo_log import log as logging
 from oslo_middleware import base
+from tricircle.common import constants as cons
 import webob
 
 LOG = logging.getLogger(__name__)