Docker fix healthcheck; allow modules; cleanup; set uid The docker healthcheck was hardcoded to check the /issues/ tracker. Replace healthcheck with one that looks for the tracker names on the roundup-server command line and checks the first one. During build, additional modules can be specified using --build-arg="pip_mod=requests setproctitle". This lets the user add modules unique to the tracker without having to 'docker commit' a new image from a running container. Use --build-arg="roundup_uid=2000" to change the uid roundup runs as. The default is 1000. This is done at build time, not run time. Remove the sphinx package. All the dependent packages were removed before, but sphinx wasn't. This led to spurious warnings fom the pip dependency resolver. Update docs with changes.

Debugging Aids
--------------

Try turning on logging of DEBUG level messages. This may be done a number
of ways, depending on what it is you're testing:

1. If you're testing the database unit tests, then set the environment
   variable ``LOGGING_LEVEL=DEBUG``. This may be done like so:

    LOGGING_LEVEL=DEBUG python -m pytest test/

   This variable replaces the older HYPERDBDEBUG environment var.

2. If you're testing a particular tracker, then set the logging level in
   your tracker's ``config.ini``.

SENDMAILDEBUG
=============

Set to a filename and roundup will write each email message
that it sends to that file instead to the internet. 
This environment variable is independent of the python -O flag.