windows & mac jobs

.travis.yml

@@ -1,12 +1,22 @@
 language: python
-os:
-  - "linux"
-  - "osx"
-  - "windows"
-python:
-  - "3.6"  # Current default Python on Travis CI
-  - "3.7"
-  - "3.8"
+jobs:
+  include:
+    - name: "Python on Xenial Linux"
+      python:
+        - "3.6"
+        - "3.7"
+        - "3.8"
+    - name: "Python 3.7.4 on macOS"
+      os: osx
+      osx_image: xcode12u  # Python 3.7.4 running on macOS 10.14.4
+      language: shell      # 'language: python' is an error on Travis CI macOS
+    - name: "Python 3.8.0 on Windows"
+      os: windows          # Windows 10.0.17134 N/A Build 17134
+      language: shell      # 'language: python' is an error on Travis CI Windows
+      before_install:
+        - choco install python --version 3.8.0
+        - python -m pip install --upgrade pip
+      env: PATH=/c/Python38:/c/Python38/Scripts:$PATH
 before_install:
   - pip install -U pip
   - pip install -U pytest