daniel@daydream:~$ sudo apport-retrace -S sb -g /var/crash/_usr_bin_Xorg.0.crash 
Traceback (most recent call last):
  File "/usr/bin/apport-retrace", line 301, in <module>
    options.dynamic_origins)
  File "/usr/lib/python2.7/dist-packages/apport/sandboxutils.py", line 202, in make_sandbox
    architecture=report.get('Architecture'), origins=origins)
  File "/usr/lib/python2.7/dist-packages/apport/packaging_impl.py", line 731, in install_packages
    self.set_mirror(self._get_primary_mirror_from_apt_sources(apt_sources))
  File "/usr/lib/python2.7/dist-packages/apport/packaging_impl.py", line 1113, in _get_primary_mirror_from_apt_sources
    with open(apt_sources) as f:
IOError: [Errno 2] No such file or directory: u'sb/Ubuntu 15.10/sources.list'