[docs] [issue37503] Queue.join(): Broken example in documentation

[Marco Dickert]

New submission from Marco Dickert <marco at misterunknown.de>:

I guess I found a bug in the documented Queue.join() example [1].

The problem is the break condition for the while loop of the worker. If the item is None, the loop breaks, but the worker never calls item.task_done(). Thus the q.join() statement never returns, because the last task (None) remains unfinished.

This should solve the issue:

```
if item is None:
  item.task_done()
  break
```

[1] https://docs.python.org/3/library/queue.html#queue.Queue.join

----------
assignee: docs at python
components: Documentation
messages: 347310
nosy: docs at python, misterunknown
priority: normal
severity: normal
status: open
title: Queue.join(): Broken example in documentation
versions: Python 3.5, Python 3.6, Python 3.7

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue37503>
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