ubuntu-bug autocomplete shows an egrep error

[Juan Simón]

I write, in console, "ubuntu-bug ubu" and press TAB key.
It shows an error:

$ apport-bug ubuegrep: /usr/share/apport/symptoms/dist-upgrade.py@: No such file or directory
egrep: /usr/share/apport/symptoms/release-upgrade.py@: No such file or directory
Display all 108 possibilities? (y or n)

But this file exists:

$ ll /usr/share/apport/symptoms/release-upgrade.py
lrwxrwxrwx 1 root root 26 may 23 21:45 /usr/share/apport/symptoms/release-upgrade.py -> ubuntu-release-upgrader.py

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: apport 2.9.2-0ubuntu8.3
Uname: Linux 3.11.3-20131002-i7 x86_64
NonfreeKernelModules: nvidia
ApportLog:

ApportVersion: 2.9.2-0ubuntu8.3
Architecture: amd64
Date: Wed Oct 2 15:51:26 2013
InstallationDate: Installed on 2013-02-11 (233 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Release amd64 (20121017.5)
MarkForUpload: True
PackageArchitecture: all
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=es_ES.UTF-8
 SHELL=/bin/bash
SourcePackage: apport
UpgradeStatus: Upgraded to raring on 2013-04-26 (159 days ago)