Drop python 2.7 support and testing

Change-Id: I3ff7a714d5fd61edd72e00c7a454c81724844f99
Closes-bug: #1853372
diff --git a/test-requirements.txt b/test-requirements.txt
index f53437e..af89592 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -6,8 +6,7 @@
 
 coverage!=4.4,>=4.0 # Apache-2.0
 python-subunit>=1.0.0 # Apache-2.0/BSD
-sphinx!=1.6.6,!=1.6.7,>=1.6.2,<2.0.0;python_version=='2.7'  # BSD
-sphinx!=1.6.6,!=1.6.7,>=1.6.2;python_version>='3.4'  # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2 # BSD
 oslotest>=3.2.0 # Apache-2.0
 testrepository>=0.0.18 # Apache-2.0/BSD
 testtools>=2.2.0 # MIT