fixup! fixup! fixup! fixup! Fix Travis when SIX_VERSION isn't specificed

Author: gsnedders

requirements-install.sh

@@ -5,6 +5,8 @@ if [[ $USE_OPTIONAL != "true" && $USE_OPTIONAL != "false" ]]; then
   exit 1
 fi
 
+pip install -U setuptools wheel pip
+
 pip install -U -r requirements-test.txt
 
 if [[ $USE_OPTIONAL == "true" ]]; then