[libvirt] [jenkins-ci PATCH] lcitool: Raise Error instead of Exception

[Erik Skultety]

On Mon, Mar 11, 2019 at 07:11:49PM +0100, Andrea Bolognani wrote:
> On Mon, 2019-03-11 at 17:55 +0000, Daniel P. Berrangé wrote:
> > On Mon, Mar 11, 2019 at 06:48:11PM +0100, Andrea Bolognani wrote:
> > > This results in
> > >
> > >   $ ./lcitool dockerfile dockerfile -x foo libvirt-debian-9 libvirt
> > >   FROM debian:9
> > >   ./lcitool: Unsupported architecture ppc64el
> > >
> > > being printed on error, instead of the much nastier
> > >
> > >   $ ./lcitool dockerfile dockerfile -x foo libvirt-debian-9 libvirt
> > >   FROM debian:9
> > >   Traceback (most recent call last):
> > >     File "./lcitool", line 704, in <module>
> > >       Application().run()
> > >     File "./lcitool", line 699, in run
> > >       args.func(args)
> > >     File "./lcitool", line 643, in _action_dockerfile
> > >       deb_arch = Util.native_arch_to_deb_arch(args.cross_arch)
> > >     File "./lcitool", line 126, in native_arch_to_deb_arch
> > >       raise Exception("Unsupported architecture {}".format(native_arch))
> > >   Exception: Unsupported architecture foo
> >
> > I'm curious why the "Error" class exists at all ? It doesn't seem
> > to add anything that the normal "Exception" class can't do, and
> > leads to bugs like the one here.
>
> I seem to understand you're not supposed to use Exception directly,
> but rather define your own exception types:
>
>   https://docs.python.org/3/tutorial/errors.html#user-defined-exceptions
>
> I remember reading more about this, but I can't find the source
> right now.

Hmm, I've been told to subclass the Exception only if the module you're writing
is supposed to be a library/package someone else would like to depend on. But
in case of a standalone cli app (which this is), Exception should be all we
need.

Erik