bug#27215: break-at-source doesn't seem to work

[Maxim Cournoyer]

Hello Guile!

I'm trying to get proficient at debugging Guile programs, and while
trying things I noticed that the ,break-at-source interactive command
doesn't seem to work. See the following Geiser session:

--8<---------------cut here---------------start------------->8---
GNU Guile 2.2.2
Copyright (C) 1995-2017 Free Software Foundation, Inc.

Guile comes with ABSOLUTELY NO WARRANTY; for details type `,show w'.
This program is free software, and you are welcome to redistribute it
under certain conditions; type `,show c' for details.

Enter `,help' for help.
scheme@(guile-user)> ,m (guix scripts environment)
scheme@(guix scripts environment)> ,bs 
"/home/maxim/src/guix/scripts/environment.scm" 543
While executing meta-command:
ERROR: No procedures found at ~a:~a. 
"/home/maxim/src/guix/scripts/environment.scm" 543
scheme@(guix scripts environment)> ,break guix-environment
Trap 1: Breakpoint at #<procedure guix-environment args>.
--8<---------------cut here---------------end--------------->8---

There are two things to notice here:

1. The ,bs (break-at-source) command couldn't find the
(guix-environment) proceduce located exactly on line 543 of the
environment.scm file, although ,break guix-environment could.

2. The error message is not formatted right.

It might or might not be related to
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=26027 as suggested by
spk121 on #guile.

Maxim