Just raise it, let the caller figure out what to do.

This reverts commit 1118325ec5f7aec7b2d50867848f4b2d51c59b41.

The output of 'git branch' is not guaranteed to remain constant.  Using
the for-each-ref plumbing command should work reliably for longer.

The bash completion 'filenames' option prevents proper completion of
local refs like tmz/f13.

On systems with bash-completion >= 1.2, this should have little effect
because the _filedir command sets the option as needed (or emulates it
on older bash releases that lack compopt).

On systems with older bash-completion (like EL-5 currently), there is a
minor downside in that filename completion won't append trailing slashes
to directories without the 'filenames' option.  Ideally, bash-completion
will be updated on EL-5 and this minor inconvenience will vanish
sometime soon.

The _filedir function is a bit more robust than using compgen directly.
A wrapper function is used to filter out .git directories from results.

Make sure that WARN, ERROR, and CRITICAL go to stderr, and that DEBUG
and INFO go to stdout.  This involves more configuration than it aught
to, but that's python logging for ya.

It's of my opinion that only errors should go to stderr.  For that
reason I'll have all logger stuff to go stdout and any errors I'll use
print() on.

Again this is just because rpmbuild does some stupid things.