stubtest: run on py39 (#4110)

I've made mistakes in #4069 and #4010 that would have been caught by
this, so seems worth it to add now, and continue to remove from
whitelists.
Note that we run with --ignore-missing-stub in CI, so this whitelist
isn't all the changes we'd need to fully support Python 3.9

Co-authored-by: hauntsaninja <>

.travis.yml

@@ -29,6 +29,10 @@ jobs:
     - name: "flake8"
       install: pip install -r requirements-tests-py3.txt
       script: flake8
+    - name: "stubtest py39"
+      python: 3.9-dev
+      install: pip install -U git+git://github.com/python/mypy@b3d43984
+      script: ./tests/stubtest_test.py
     - name: "stubtest py38"
       python: 3.8
       install: pip install -U git+git://github.com/python/mypy@b3d43984
@@ -45,8 +49,3 @@ jobs:
       python: 3.5
       install: pip install -U git+git://github.com/python/mypy@b3d43984
       script: ./tests/stubtest_test.py
-  allow_failures:
-    - name: "stubtest py39"
-      python: 3.9-dev
-      install: pip install -U git+git://github.com/python/mypy@b3d43984
-      script: ./tests/stubtest_test.py