[py-dev] Logging in the py library

[Grig Gheorghiu]

I think it would be useful to implement logging in the py library via
the 'logging' module, which is supposed to be thread-safe. Currently
there are one-off implementations of logging/tracing scattered across
source files (for example the trace method in execnet/gateway.py). It
would be nice to have a uniform way of capturing debug information with
various levels of severity (debug, info, warning, error, critical). 

If you think this is a good idea, let me know. I'm willing to take a
stab at the implementation.

Grig