gh-150116 Remove dead try/except in asyncio.Lock._wake_up_first

[deadlovelll]

asyncio.Lock._wake_up_first had a try/except StopIteration block guarding next(iter(self._waiters)):

  def _wake_up_first(self):
      if not self._waiters:
          return
      try:
          fut = next(iter(self._waiters))
      except StopIteration:
          return
      ...

The except branch is unreachable. The preceding early return ensures self._waiters is a non-empty collections.deque

After:

  def _wake_up_first(self):
      if not self._waiters:
          return
      fut = next(iter(self._waiters))
      if not fut.done():
          fut.set_result(True)

No behavior change.

• Issue: Remove dead try/except StopIteration in asyncio.Lock._wake_up_first #150116

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[JelleZijlstra]

Is it possible for another thread to add something to the container between the two checks?

[deadlovelll]

Is it possible for another thread to add something to the container between the two checks?

Thanks for marking it. But asyncio primitives are not thread-safe. The official documentation says: link