Fix sphinx-docs job for stable branch

build-openstack-sphinx-docs jobs fail on stable branches due to the new
pip version 10 introduces some previously Warning as Error: in case of
calling "pip install" without any package name, the command fails.
tox_install.sh is called during docs job without any package passed to pip.

Change-Id: I860a8776bb32e8e05abd914110ca8df24d869bd2

doc/source/conf.py

@@ -64,7 +64,7 @@ copyright = u'%s, OpenStack Foundation' % datetime.date.today().year
 # The short X.Y version.
 version = subprocess.Popen(['sh', '-c', 'cd ../..; python setup.py --version'],
                            stdout=subprocess.PIPE).stdout.read()
-version = version.strip()
+version = str(version).strip()
 # The full version, including alpha/beta/rc tags.
 release = version
 

tools/tox_install.sh

@@ -26,5 +26,10 @@ pip install -c"$localfile" openstack-requirements
 # install will be constrained and we need to unconstrain it.
 edit-constraints "$localfile" -- "$CLIENT_NAME"
 
+if [ -z "$@" ]; then
+    echo "No packages to be installed."
+    exit 0
+fi
+
 pip install -c"$localfile" -U "$@"
 exit $?