Switch to nightly builds of Python 3.9 because travis still hasn't added the Python 3.9.0 release.

dgrunwald · dgrunwald · commit e87375e65e42 · 2020-10-26T11:56:26.000+01:00
diff --git a/.travis.yml b/.travis.yml
@@ -6,7 +6,7 @@ python:
   - "3.6"
   - "3.7"
   - "3.8"
-  - "3.9"
+  - "3.9-dev"
 env:
   - RUST_VERSION=1.32.0
   - RUST_VERSION=stable
