…ythonGH-2470)

* Clear potential ref cycle between Process and Process target

Besides Process.join() not being called, this was an indirect cause of bpo-30775.
The threading module already does this.

* Add issue reference.
(cherry picked from commit 79d37ae)

pitrou deleted the backport-79d37ae-3.6 branch

vstinner changed the title [3.6] Clear potential ref cycle between Process and Process target (GH-2470) [3.6] bpo-30775: Clear potential ref cycle between Process and Process target (GH-2470)