Use pyenv instead of deadsnakes on macOS

[changelog skip]

.travis.yml

@@ -1,8 +1,7 @@
 matrix:
   include:
   - os: osx
-    osx_image: xcode8.1
-    # See also: https://github.com/Homebrew/homebrew-core/issues/6949
+    osx_image: xcode11.3
   - os: linux
     language: python
     python: pypy
@@ -33,20 +32,22 @@ install:
   |
   if [[ "$TRAVIS_OS_NAME" = "linux" ]]; then
     pip install --upgrade pip setuptools
-    pip install --upgrade tox-travis docutils twine
+    pip install --upgrade tox-travis twine
   elif [[ "$TRAVIS_OS_NAME" = "osx" ]]; then
     brew update || true
     brew upgrade || true
-    brew update || true
-    brew tap drolando/homebrew-deadsnakes
-    brew install python33 python34 python35 python3 pypy
-    pip3 install --upgrade pip setuptools
-    pip3 install --user tox docutils
+    pyenv install 2.7.17 3.7.6 3.6.10 3.5.9 3.4.9 pypy2.7-7.3.0 pypy3.6-7.3.0
+    pyenv global 2.7.17 3.7.6 3.6.10 3.5.9 3.4.9 pypy2.7-7.3.0 pypy3.6-7.3.0
+    pip2 install -U pip setuptools virtualenv
+    curl https://raw.githubusercontent.com/mitsuhiko/pipsi/master/get-pipsi.py \
+      | python2 - --no-modify-path
+    "$HOME/.local/bin/pipsi" install tox
+    "$HOME/.local/venvs/tox/bin/pip" install tox-pyenv
   fi
 script:
 - |
   if [[ "$TRAVIS_OS_NAME" = "osx" ]]; then
-    export PATH="$(python3 -m site --user-base)/bin:$PATH"
+    export PATH="$HOME/.local/bin:$(python2 -m site --user-base)/bin:$PATH"
   fi
   tox -- -O --github-access-token="$GITHUB_ACCESS_TOKEN"
   [[ "$TRAVIS_PYTHON_VERSION" = pypy* ]] || tox -e lint