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 <>

tests/stubtest_test.py

@@ -3,7 +3,7 @@
 
 stubtest is a script in the mypy project that compares stubs to the actual objects at runtime.
 Note that therefore the output of stubtest depends on which Python version it is run with.
-In typeshed CI, we run stubtest with each Python minor version from 3.5 through 3.8 inclusive.
+In typeshed CI, we run stubtest with each Python minor version from 3.5 through 3.9 inclusive.
 
 We pin the version of mypy / stubtest we use in .travis.yml so changes to those don't break
 typeshed CI.
@@ -35,7 +35,7 @@ def run_stubtest(typeshed_dir: Path) -> int:
         "--whitelist",
         str(whitelist_dir / version_whitelist),
     ]
-    if sys.version_info < (3, 8):
+    if sys.version_info < (3, 9):
         # As discussed in https://github.com/python/typeshed/issues/3693, we only aim for
         # positional-only arg accuracy for the latest Python version.
         cmd += ["--ignore-positional-only"]
@@ -46,7 +46,7 @@ def run_stubtest(typeshed_dir: Path) -> int:
         print(
             "\nNB: stubtest output depends on the Python version (and system) it is run with. "
             "See README.md for more details.\n"
-            "NB: We only check positional-only arg accuracy for Python 3.8.\n"
+            "NB: We only check positional-only arg accuracy for Python 3.9.\n"
             "If stubtest is complaining about 'unused whitelist entry' after your fix, please "
             "remove the entry from the whitelist file. Note you may have to do this for other "
             "version-specific whitelists as well. Thanks for helping burn the backlog of errors!\n"