Run Travis CI tests in OS X based environment (PR #26)

* PoC of running tests under MacOS
* reusable YAML anchors reduce config duplication dramatically
* completely pyenv based python installations

.travis.yml

@@ -9,12 +9,8 @@ python:
 - 3.6
 - nightly
 _base_envs:
-- &pypy_base
-  python: pypy
-  env:
-  - PYPY_VERSION=pypy2-5.7.1
-  - PYENV_ROOT="$HOME/.pyenv"
-  - PATH="$PYENV_ROOT/bin:$PATH"
+- &linux_base
+  os: linux
   dist: trusty
   sudo: required
   addons:
@@ -34,8 +30,14 @@ _base_envs:
       - libncursesw5-dev
       - xz-utils
       - tk-dev
+- &pyenv_base
+  python: pypy
+  env:
+  - PYTHON_VERSION=pypy2-5.7.1
+  - &env_pyenv PYENV_ROOT="$HOME/.pyenv"
+  - &env_path PATH="$PYENV_ROOT/bin:$PATH"
   before_install:
-  - |
+  - &ensure_pyenv_installed |
     if [ -f "$PYENV_ROOT/bin/pyenv" ]
     then
       eval "$(pyenv init -)"
@@ -47,26 +49,91 @@ _base_envs:
       eval "$(pyenv init -)"
       eval "$(pyenv virtualenv-init -)"
     fi
-  - pyenv install --skip-existing --keep --verbose "$PYPY_VERSION"
-  - pyenv shell "$PYPY_VERSION"
-  - python --version
+  - &install_python pyenv install --skip-existing --keep --verbose "$PYTHON_VERSION"
+  - &switch_python pyenv shell "$PYTHON_VERSION"
+  - &python_version python --version
+- &linux_python_base
+  <<: *linux_base
+  <<: *pyenv_base
+- &osx_python_base
+  <<: *pyenv_base
+  os: osx
+  language: generic
+  before_install:
+  - brew update
+  - brew install readline xz
+  - *ensure_pyenv_installed
+  - *install_python
+  - *switch_python
+  - *python_version
+  before_cache:
+  - brew --cache
 matrix:
   fast_finish: true
   allow_failures:
   - env: TOXENV=pre-commit-pep257
   include:
-  - <<: *pypy_base
+  - <<: *linux_python_base
     python: pypy
     env:
-    - PYPY_VERSION=pypy2-5.7.1
-    - PYENV_ROOT="$HOME/.pyenv"
-    - PATH="$PYENV_ROOT/bin:$PATH"
-  - <<: *pypy_base
+    - PYTHON_VERSION=pypy2-5.7.1
+    - *env_pyenv
+    - *env_path
+  - <<: *linux_python_base
     python: pypy3
     env:
-    - PYPY_VERSION=pypy3.5-5.7.1-beta
-    - PYENV_ROOT="$HOME/.pyenv"
-    - PATH="$PYENV_ROOT/bin:$PATH"
+    - PYTHON_VERSION=pypy3.5-5.7.1-beta
+    - *env_pyenv
+    - *env_path
+  - <<: *osx_python_base
+    python: 2.6
+    env:
+    - PYTHON_VERSION=2.6.9
+    - *env_pyenv
+    - *env_path
+  - <<: *osx_python_base
+    python: 2.7
+    env:
+    - PYTHON_VERSION=2.7.13
+    - *env_pyenv
+    - *env_path
+  - <<: *osx_python_base
+    python: 3.3
+    env:
+    - PYTHON_VERSION=3.3.6
+    - *env_pyenv
+    - *env_path
+  - <<: *osx_python_base
+    python: 3.4
+    env:
+    - PYTHON_VERSION=3.4.6
+    - *env_pyenv
+    - *env_path
+  - <<: *osx_python_base
+    python: 3.5
+    env:
+    - PYTHON_VERSION=3.5.3
+    - *env_pyenv
+    - *env_path
+  - <<: *osx_python_base
+    python: 3.6
+    env:
+    - PYTHON_VERSION=3.6.1
+    - *env_pyenv
+    - *env_path
+  - <<: *osx_python_base
+    python: nightly
+    env:
+    - PYTHON_VERSION=3.7-dev
+    - *env_pyenv
+    - *env_path
+  - <<: *osx_python_base
+    python: pypy2-5.7.1
+    env:
+    - PYTHON_VERSION=pypy2-5.7.1
+    - *env_pyenv
+    - *env_path
+  # pypy3.5-5.7.1-beta fails under OS X because it's unsupported (PR #26)
   - python: 3.6
     env: TOXENV=pre-commit
   - python: 3.6
@@ -75,6 +142,7 @@ cache:
   pip: true
   directories:
   - $HOME/.pre-commit
+  - $HOME/Library/Caches/Homebrew
 before_install:
 - "if [[ $TRAVIS_PYTHON_VERSION == 'pypy3' ]]; then . .travis/replace-pypy3 ; fi"
 install: