exception prints literal {exception.args} because it's not an f-string

[matthewwiese]

Recently I encountered the following error while debugging some code:

redis.exceptions.ResponseError: Command # 1 (FT.SEARCH geneIdx...) of pipeline caused error: {exception.args}

I went down a bit of a rabbit hole before realizing the solution, and I think if exception.args were actually printed I might have discovered it sooner. Regardless, this is a minor bug that ought to be fixed.

Code in question: https://github.com/redis/redis-py/blob/master/redis/asyncio/client.py#L1587

I will open a PR in a sec.