Update jobs for 2.7, 3.7, 3.8

.travis.yml

@@ -5,26 +5,40 @@ matrix:
     - python: 2.7
       name: "Test Python 2.7"
       env: TOXENV=py27
+      before_install:
+        - sudo apt-get update
+        - sudo apt-get install -y build-essential python-dev libgtk-3-dev libjpeg-dev libtiff-dev      
       install: pip install tox
-      script: tox
+      script: tox -vvvvv
     - python: 3.6
       name: "Test Python 3.6"
       env: TOXENV=py36
-      install: pip install tox
       before_install:
         # Install neccessary Linux dependencies to build wxPython.
         #   See: https://github.com/wxWidgets/Phoenix/blob/master/.azure/ci-linux-job.yml
         - sudo apt-get update
         - sudo apt-get install -y build-essential python3-dev libgtk-3-dev libjpeg-dev libtiff-dev
+      install: pip install tox
       script:
         # Pass -vvv to pip through tox because wxPython can take ~20min to build and
         # Travis CI thinks that the build has stalled unless build progress is output.
         - tox -vvvvv
     - python: 3.7
       name: "Test Python 3.7"
       env: TOXENV=py37
+      before_install:
+        - sudo apt-get update
+        - sudo apt-get install -y build-essential python3-dev libgtk-3-dev libjpeg-dev libtiff-dev
+      install: pip install tox
+      script: tox -vvvvv
+    - python: 3.8
+      name: "Test Python 3.8"
+      env: TOXENV=py38
+      before_install:
+        - sudo apt-get update
+        - sudo apt-get install -y build-essential python3-dev libgtk-3-dev libjpeg-dev libtiff-dev
       install: pip install tox
-      script: tox
+      script: tox -vvvvv
     - python: 3.6
       name: "Check formatting"
       install: pip install black isort