A new class var `tuple[Exception]` such that the err set can be reffed
externally as needed for catching other similar pub-sub/IPC failures in
other (related) real-time sub-systems.
Also added some now-masked logging for debugging live-feed stream reading
issues that should ONLY be used for debugging since they'll greatly
degrade HFT perf. Used the new `log.mk_repr()` stuff (that one day we
should prolly pull from `modden` as a dep) for pretty console emissions.
Since now `tractor` will raise this native `trio`-exc translated from
a `Stop` msg when the peer gracefully terminates a `tractor.MsgStream`.
Just `info()` log in such cases versus continuing to warn for the
others.
Tyler Goodlet