allow .tac files to configure logging behavior

[radix]

It would be useful to allow .tac files to configure logging behavior by specifying in the .tac file the observer to be used.

Of course, twistd should also have some sort of user interface for customizing logging behavior, which is being tracked in #638.

[radix]

(In [25356]) Branching to 'configure-log-observer-in-tacs-3534'

[radix]

Ok, here's basically the same branch as in #638 but without the --logger stuff.

Please review.

[therve]

1. Some flakes:

   doc/core/examples/twistd-logging.tac:10: 'sys' imported but unused
   twisted/application/app.py:9: 'namedAny' imported but unused
   

2. In application.xhtml, the example you give is correct, but doesn't bring much against the -l option of twistd. Maybe you could use a DailyLogFile to show an advantage?
3. The twistd-logging.tac example is nice, but it shows bad usage of logging: it doesn't call flush on the log file, and it doesn't use untilConcludes.
4. The example tac file needs to be referenced in examples/index.xhtml

That's it!

[therve]

Build results here:  http://buildbot.twistedmatrix.com/boxes-supported?branch=branches/configure-log-observer-in-tacs-3534&num_builds=1

[radix]

Thanks therve.

1. fixed
2. ok, I changed it to use DailyLogFile.
3. Ok, I made it call flush and use untilConcludes on both the write and flush call, and even explained why.
4. fixed, and organized a new Logging section in the example index.

[therve]

Awesome, please merge.

[radix]

(In [25379]) Merge configure-log-observer-in-tacs-3534

Author: radix Reviewer: therve Fixes: #3534

Now it's possible to specify the log observer used by twistd in a .tac file by setting the ILogObserver component on the application.