Fix piping of version

tests/test_supported_wheels.sh

@@ -26,7 +26,8 @@ fi
 
 # Test that wheels for versions other than our own, not supported.
 if [ $(uname) == 'Darwin' ]; then
-    our_ver=$(python --version | awk '{print $2}' | awk -F '.' '{print $1$2}')
+    # 2>&1 because Python 2.7 version goes to stderr
+    our_ver=$(python --version 2>&1 | awk '{print $2}' | awk -F '.' '{print $1$2}')
     other_ver=$([ "$our_ver" == "37" ] && echo "38" || echo "37")
     good_whl="tornado-5.1-cp${our_ver}-cp${our_ver}m-macosx_10_9_x86_64.whl"
     bad_whl="tornado-5.1-cp${other_ver}-cp${other_ver}m-macosx_10_9_x86_64.whl"