Code review comment for lp:~jtv/maas/db-fixture

As for van.pg, it's attractive to have this job done by code from others but several things made me decide against it:

 * As far as I can tell, it's not packaged for Ubuntu. Dealing with that could be more trouble than rolling our own.

 * It depends on testresources, which is in universe.

 * The documentation didn't tell me what I needed to know, so I got lazy and just wrote my own.

 * Both django and van.pg try to create the test databases themselves, so there's a bit of overlap.

 * We have more flexibility to tweak our own, purpose-built code. For instance, our code can create a non-disposable database if necessary.