Async context manager

Usecase:

c = Counter("errors_count")

@c.count_exceptions()
def foo():  # counter = 1
      raise Exception()

@c.count_exceptions()
async def foo_async(): # counter still 1
      await sleep(1)
      raise Exception()

Quick search in project did nothing to me.

It would be cool if counter (and other objects) would handle this right out of the box, especially if we're talking about metrics for web world.

首先跟踪 Counter 的实现及其 count_exceptions() 装饰器，然后检查 foo_async 示例的行为。定义所支持的异步上下文管理器或装饰器行为，并验证异步示例中的异常会按要求更新计数器。