Support stderr

[analytically]

At the moment it's not writing stderr events to Supervisor's stderr.

[coderanger]

Make sure you have stderr events enabled via stderr_events_enabled = true.

[lkwg82]

so this is closable?

[mrmachine]

I think it writes stderr to supervisor's stdout (with "stderr" in the prefix), which doesn't seem right.

[whereisaaron]

In each 'program' section forward both stdout and stderr events to the stdout handler. The handler will pass on both types of event to stdout on supervisord, annotated with a prefix that says 'stdout' or 'stderr'. You can disable log files since they just duplicate supervisord output.

stdout_events_enabled = true
stderr_events_enabled = true
stdout_logfile = NONE
stderr_logfile = NONE