Updated from global requirements

Change-Id: Ib3ea4225636bfa815f7cf60481d2adc07077123c

Author: OpenStack Proposal Bot

requirements.txt

@@ -5,7 +5,7 @@ pbr!=2.1.0,>=2.0.0 # Apache-2.0
 six>=1.9.0 # MIT
 
 Babel!=2.4.0,>=2.3.4 # BSD
-cliff>=2.3.0 # Apache-2.0
+cliff>=2.6.0 # Apache-2.0
 keystoneauth1>=2.18.0 # Apache-2.0
 openstacksdk>=0.9.14 # Apache-2.0
 osc-lib>=1.2.0 # Apache-2.0