test: add Windows to GitHub Actions testing (#1996)

PR-URL: #1996
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>

.github/workflows/Python_tests.yml

@@ -1,4 +1,3 @@
-# TODO: Line 14, enable os: windows-latest
 # TODO: Line 15, enable python-version: 3.5
 # TODO: Line 36, enable pytest --doctest-modules
 
@@ -11,7 +10,7 @@ jobs:
       fail-fast: false
       max-parallel: 15
       matrix:
-        os: [macos-latest, ubuntu-latest]  # , windows-latest]
+        os: [macos-latest, ubuntu-latest, windows-latest]
         python-version: [2.7, 3.6, 3.7, 3.8]  # 3.5,
     steps:
       - uses: actions/checkout@v1
@@ -30,7 +29,12 @@ jobs:
           flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
           # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
           flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
-      - name: Test with pytest
+      - name: Test with pytest (Linux and macOS)
+        if: matrix.os != 'windows-latest'
         run: pytest
+      - name: Test with pytest (Windows)
+        if: matrix.os == 'windows-latest'
+        shell: bash
+        run: GYP_MSVS_VERSION=2015 GYP_MSVS_OVERRIDE_PATH="C:\\Dummy" pytest
       # - name: Run doctests with pytest
       #   run: pytest --doctest-modules