* reap_children() now sets environment_altered to True to detect bugs
  using python3 -m test --fail-env-changed
* Replace bare "except:" with "except OSError:" in reap_children()
* Write an unit test for reap_children() using a timeout of 60
  seconds

…ect test_subprocess"

This reverts commit 5b6f64a510460d766984f95c6dc747dc48210b04.

bpo-31151: socketserver.ForkingMixIn.server_close() now waits until
all child processes completed to prevent leaking zombie processes.