message: Actually implement the TestQueues.py workaround
  The code commited in r355764 didn't do what I want as I typed GetThreadID
  instead of GetQueueID. This commit contains a (hopefully) better version
  of the workaround.
diff: @@ -337,6 +337,10 @@ class TestQueues(TestBase):
  queue_performer_2 = q
  if q.GetName() == "com.apple.work_performer_3":
  queue_performer_3 = q
  + if q.GetName() == "com.apple.main-thread":
  + if q.GetNumThreads() == 0:
  + print("Cannot get thread <=> queue associations")
  + return
  self.assertTrue(
  queue_submittor_1.IsValid() and queue_performer_1.IsValid() and queue_performer_2.IsValid() and queue_performer_3.IsValid(),
  @@ -357,11 +361,6 @@ class TestQueues(TestBase):
  queue_performer_2, 1, 9999)
  self.check_running_and_pending_items_on_queue(queue_performer_3, 4, 0)
  - for th in process.threads:
  - if th.GetThreadID() == lldb.LLDB_INVALID_QUEUE_ID:
  - print("Cannot get thread <=> queue associations")
  - return
  -
  self.check_number_of_threads_owned_by_queue(queue_submittor_1, 1)
  self.check_number_of_threads_owned_by_queue(queue_performer_1, 1)
  self.check_number_of_threads_owned_by_queue(queue_performer_2, 1)
  