message: Additional Travis improvements
  Select Linux and OSX images explicitly.
  Simplify logic for Python version selection.
  Reduce parallel jobs for performance.
diff: language: cpp
  +dist: xenial
  +osx_image: xcode10
  addons:
  apt:
  @@ -41,14 +43,14 @@ matrix:
  env: MATRIX_EVAL="CC=clang-8 && CXX=clang++-8 && PY=3"
  before_install:
  + - export PY=2
  - eval "${MATRIX_EVAL}"
  - - export PY=${PY:-"2"}
  script:
  - mkdir build
  - cd build
  - cmake -DMATERIALX_BUILD_PYTHON=ON -DMATERIALX_BUILD_VIEWER=ON -DMATERIALX_PYTHON_VERSION=$PY -DMATERIALX_INSTALL_PYTHON=OFF -DMATERIALX_WARNINGS_AS_ERRORS=ON ..
  - - cmake --build . --target install -- -j4
  + - cmake --build . --target install -- -j2
  - ctest -VV --output-on-failure
  - export PYTHONPATH=$PYTHONPATH:$PWD/installed/python
  - cmake -E chdir ../python/MaterialXTest python$PY main.py
  