On Ubuntu 17.10, the Backups application fails with this error:

Traceback (most recent call last):
  File "/usr/bin/duplicity", line 1546, in <module>
  File "/usr/bin/duplicity", line 1540, in with_tempdir
  File "/usr/bin/duplicity", line 1391, in main
  File "/usr/bin/duplicity", line 1416, in do_backup
TypeError: __init__() takes exactly 4 arguments (3 given)

I think this might be a Python 2/3 problem, but it appears other users on 17.10 have deja-dup working.

I've tried reinstalling deja-dup and duplicity, same problem.

Duplicity version: 0.7.12-1ubuntu1
Deja-dup version: 36.3-0ubuntu0.1


I was suspecting that for some reason Duplicity wasn't passing self to the class, but in the code the offending line is:

col_stats = collections.CollectionsStatus(globals.backend,

Meaning that it's probably not a Python version error because it did indeed pass three arguments to the class.

Now in the CollectionsStatus class, the help says:

Help on class CollectionsStatus in module duplicity.collections:

class CollectionsStatus
 |  Hold information about available chains and sets
 |  Methods defined here:
 |  __init__(self, backend, archive_dir, action)
 |      Make new object.  Does not set values

Meaning that it should definitely be passing 4 arguments, including self.

I have a feeling I know what's going wrong. I often use a script to update all of my Python modules, so I bet that class got changed somewhere along the line and the versions of Duplicity (the shell script) and its Python module are mismatched.

  • 2
    Did you install some version of Python manually? – muru Jan 28 '18 at 1:50
  • @muru not that I remember ... aptitude show python python3 says my Python versions are 2.7.14-2ubuntu1 and 3.6.3-0ubuntu2. Maybe I should try to find deja-dup's source and check if it's targeting a specific version of Python that's bugged, since those two are working fine. – imyxh Jan 28 '18 at 5:25
  • 1
    /usr/lib/python2.7/dist-packages/duplicity/collections.py shows CollectionsStatus.__init__ actually takes 3 arguments as expected. – muru Jan 28 '18 at 5:44
  • @muru Ah, I just finished writing up something about that in my edits section. I guess I'll have to downgrade the Python module of Duplicity. – imyxh Jan 28 '18 at 5:49

Apparently, I had Duplicity Python module 0.7.14 and the aptitude package 0.7.12. I used sudo pip uninistall duplicity, followed by sudo aptitude reinstall duplicity and the problem's solved.

I guess I shouldn't be updating all of my Python modules at once.

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