Updated from global requirements

Change-Id: I27e6899434ac47018a6ebd140cd326e7c6cd00d9

Author: OpenStack Proposal Bot

requirements.txt

@@ -1,7 +1,7 @@
 # The order of packages is significant, because pip processes them in the order
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
-pbr>=1.6 # Apache-2.0
+pbr>=1.8 # Apache-2.0
 six>=1.9.0 # MIT
 
 Babel>=2.3.4 # BSD