bridge foolscap log events to twisted

[Brian Warner]

Practical experience with tahoe suggests that it would be useful to at least log non-trivial foolscap.logging.log.msg events to the regular twisted.python.log.msg function. This would put them into twistd.log .

The bridge needs to be careful to not cause loops, by marking everything that goes into the foolscap log (and not bridging these from the twisted observer), and also marking everything that comes out of twisted (and not bridging these into the twisted logs).

It also needs a level threshold or arbitrary function to serve as a filter.

[Brian Warner]

Done, in [999e21cd37eb8fedbd5f9048add3c43080bb699d]