Wait for the child process to terminate before ending the test, so that the
regrtest cleanup code doesn't get an error when it tries to delete the
temporary CWD.
tests that expect to be skipped if imports fail or functions don't
exist to use import_function and import_module. The ultimate goal is
to change regrtest to not skip automatically on ImportError. Checking
in now to make sure the buldbots don't show any errors on platforms
I can't direct test on.