Prune unnecessary apt-get dependencies

.travis.yml

@@ -7,17 +7,16 @@ matrix:
       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      
+        - sudo apt-get install -y build-essential python-dev libgtk-3-dev      
       install: pip install tox
       script: tox -vvvvv
     - python: 3.6
       name: "Test Python 3.6"
       env: TOXENV=py36
       before_install:
-        # Install neccessary Linux dependencies to build wxPython.
-        #   See: https://github.com/wxWidgets/Phoenix/blob/master/.azure/ci-linux-job.yml
+        # Install neccessary Linux dependencies to build wxPython from source.
         - sudo apt-get update
-        - sudo apt-get install -y build-essential python3-dev libgtk-3-dev libjpeg-dev libtiff-dev
+        - sudo apt-get install -y build-essential python3-dev libgtk-3-dev
       install: pip install tox
       script:
         # Pass -vvv to pip through tox because wxPython can take ~20min to build and
@@ -28,15 +27,15 @@ matrix:
       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
+        - sudo apt-get install -y build-essential python3-dev libgtk-3-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
+        - sudo apt-get install -y build-essential python3-dev libgtk-3-dev
       install: pip install tox
       script: tox -vvvvv
     - python: 3.6