Sync Sphinx requirement
1. Sync sphinx dependency with global requirements. It caps python 2 since
sphinx 2.0 no longer supports Python 2.7.
Change-Id: I1a5bae859f4ae998db33331126e82c7f5862a011
diff --git a/test-requirements.txt b/test-requirements.txt
index 061de95..bbf8861 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -5,4 +5,5 @@
# Hacking already pins down pep8/pycodestyle pyflakes and flake8
hacking>=1.1.0,<1.2.0 # Apache-2.0
openstackdocstheme>=1.18.1 # Apache-2.0
-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