Expose python3 env var for TravisCI.

Author: jdm

.travis.yml

@@ -24,14 +24,18 @@ addons:
     packages:
       - python
       - python@2
+      - autoconf@2.13
+      - ccache
+      - llvm
+      - yasm
 
 env:
   - FEATURES=""
   - FEATURES="--features debugmozjs"
 
 before_script:
   - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then export CC=gcc-6; export CXX=g++-6; fi
-  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew update; brew install autoconf@2.13 ccache llvm yasm; fi
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then export PYTHON3="/usr/local/opt/python3/bin/python3"; fi
 
 script:
   - ccache -z