Run linters/docs on Windows and macOS

This ensures that contributors on any of the major platforms can run our
linting and doc building checks without any changes.

.github/workflows/python-linters.yml

@@ -17,6 +17,8 @@ jobs:
       matrix:
         os:
         - ubuntu-18.04
+        - windows-latest
+        - macos-latest
         env:
         - TOXENV: docs
         - TOXENV: lint
@@ -33,11 +35,14 @@ jobs:
         path: ~/.cache/pre-commit
         key: pre-commit|${{ env.PY }}|${{ hashFiles('.pre-commit-config.yaml') }}
     - name: Pre-configure global Git settings
-      run: >-
-        tools/travis/setup.sh
+      run: |
+        git config --global user.email "pypa-dev@googlegroups.com"
+        git config --global user.name "pip"
     - name: Update setuptools and tox dependencies
-      run: >-
-        tools/travis/install.sh
+      run: |
+        python -m pip install --upgrade setuptools
+        python -m pip install --upgrade tox tox-venv
+        python -m pip freeze --all
     - name: 'Initialize tox envs: ${{ matrix.env.TOXENV }}'
       run: >-
         python -m tox --notest --skip-missing-interpreters false