Merge pull request #495 from scipopt/CI-use-python3.9

use Python-3.9 in Travis and Appveyor CI

Author: mattmilten

.travis.yml

@@ -9,6 +9,7 @@ matrix:
     - python: 3.6
     - python: 3.7
     - python: 3.8
+    - python: 3.9
       env: TRAVIS_BUILD_DOCS=$TRAVIS_TAG
       addons:
         apt:

appveyor.yml

@@ -23,6 +23,11 @@ environment:
       PIP: C:\Python38-x64\Scripts\pip
       PYTEST: C:\Python38-x64\Scripts\pytest
       TWINE: C:\Python38-x64\Scripts\twine
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      PYTHON: C:\Python39-x64
+      PIP: C:\Python39-x64\Scripts\pip
+      PYTEST: C:\Python39-x64\Scripts\pytest
+      TWINE: C:\Python39-x64\Scripts\twine
 
 
 install: