Merge pull request #4590 from radarhere/python39

Author: hugovk

.travis.yml

@@ -28,6 +28,9 @@ matrix:
 
     - python: "pypy3"
       name: "PyPy3 Xenial"
+    - python: "3.9-dev"
+      name: "3.9-dev Xenial"
+      services: xvfb
     - python: "3.8"
       name: "3.8 Xenial"
       services: xvfb