FakeLogger is broken

[Barry Warsaw]

lib/canonical/launchpad/scripts/logger.py contains a FakeLogger that claims:

    """Emulates a proper logger, just printing everything out to stdout.
    Used exclusively in doc tests."""

Sadly, it does not "emulate[] a proper logger" because it does not interpolate the positional arguments into a format string. Thus, this horror is necessary to capture logger output for tests:

    def message(self, prefix, *stuff, **kws):
        fmt = stuff[0]
        print >> self.io, prefix, fmt % stuff[1:]

We should fix FakeLogger to actually emulate the builtin logger, and we should also consolidate our testing loggers so that we have but one in our tree.