Sync Sphinx requirement
1. Sync sphinx dependency with global requirements. It caps python 2 since
sphinx 2.0 no longer supports Python 2.7.
2. Remove unncessary "=="
Change-Id: Id733fe1f513e756eb7bb2e8314bdb5dacc5dacd3
diff --git a/test-requirements.txt b/test-requirements.txt
index c0546cf..20b29f4 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -7,7 +7,8 @@
coverage!=4.4,>=4.0 # Apache-2.0
flake8-import-order==0.12 # LGPLv3
python-subunit>=1.0.0 # Apache-2.0/BSD
-sphinx!=1.6.6,!=1.6.7,>=1.6.2 # 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
oslotest>=3.2.0 # Apache-2.0
stestr>=1.0.0 # Apache-2.0
testtools>=2.2.0 # MIT