Remove Python 3 OSX Travis testing.

Pouring gcc-8.2.0.high_sierra.bottle.1.tar.gz
Error: The  step did not complete successfully

Above error needs fixing

.travis.yml

@@ -368,6 +368,10 @@ matrix:
       env: SWIGLANG=javascript ENGINE=node VER=10 CPP11=1
       sudo: required
       dist: trusty
+    # 'brew upgrade python' failure due to conflicting files: c++
+    - compiler: clang
+      os: osx
+      env: SWIGLANG=python PY3=3
     # Lots of failing tests currently
     - compiler: gcc
       os: linux