Update requirements

Change-Id: I9648255a9bed8c75902763cbcf02ec2638fabcbd
diff --git a/requirements.txt b/requirements.txt
index 01a26ba..b7e0ee0 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,10 +2,10 @@
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
 
-pbr<2.0,>=1.4
-Babel>=1.3
+pbr!=2.1.0,>=2.0.0 # Apache-2.0
+Babel!=2.4.0,>=2.3.4 # BSD
 # tempest>=6.0.0
-oslo.config>=2.3.0
-oslo.log>=1.8.0 # Apache-2.0
-six>=1.9.0
-tempest>=10.0.0
+oslo.config>=4.6.0 # Apache-2.0
+oslo.log>=3.30.0 # Apache-2.0
+six>=1.10.0 # MIT
+tempest>=17.1.0 # Apache-2.0