Traceback (most recent call last):
  File "/usr/bin/apport-retrace", line 328, in <module>
    apt_root = os.path.join(options.cache, 'system', 'apt')
  File "/usr/lib/python2.7/posixpath.py", line 77, in join
    elif path == '' or path.endswith('/'):
AttributeError: 'NoneType' object has no attribute 'endswith'