fix wstest on travis (#242)

.travis.yml

@@ -13,7 +13,7 @@ python:
 os:
 - linux
 - osx
-osx_image: xcode8.2
+osx_image: xcode9.3
 addons:
   apt:
     packages:

build/setup-wstest.sh

@@ -1,18 +1,12 @@
 #!/usr/bin/env bash
 
-if [ "$TRAVIS_OS_NAME" == "osx" ]; then
-    # Install python
-    brew update > /dev/null
-    brew install python
-fi
-
 type -p python
 python --version
 
 # Install local virtualenv
 mkdir .python
 cd .python
-curl -O https://pypi.python.org/packages/d4/0c/9840c08189e030873387a73b90ada981885010dd9aea134d6de30cd24cb8/virtualenv-15.1.0.tar.gz
+curl -OL https://pypi.python.org/packages/d4/0c/9840c08189e030873387a73b90ada981885010dd9aea134d6de30cd24cb8/virtualenv-15.1.0.tar.gz
 tar xf virtualenv-15.1.0.tar.gz
 cd ..