Description of problem:

Since updating to Fedora 24, my obnam backups no longer works, with what looks like an incompatibility between obnam and the sftp library.

Version-Release number of selected component (if applicable):

obnam-1.17-2.fc24.x86_64
python2-paramiko-1.16.0-1.fc24.noarch

How reproducible:

100%

Steps to Reproduce:
1. Configure obnam with an sftp repository
2. Run 'obnam force-lock'

Actual results:

$ obnam force-lock
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/cliapp/app.py", line 189, in _run
    self.process_args(args)
  File "/usr/lib64/python2.7/site-packages/obnamlib/app.py", line 207, in process_args
    cliapp.Application.process_args(self, args)
  File "/usr/lib/python2.7/site-packages/cliapp/app.py", line 589, in process_args
    method(args[1:])
  File "/usr/lib64/python2.7/site-packages/obnamlib/plugins/force_lock_plugin.py", line 49, in force_lock
    for client_name in repo.get_client_names():
  File "/usr/lib64/python2.7/site-packages/obnamlib/fmt_6/repo_fmt_6.py", line 149, in get_client_names
    return self._client_list.list_clients()
  File "/usr/lib64/python2.7/site-packages/obnamlib/fmt_6/clientlist.py", line 78, in list_clients
    if self.init_forest() and self.forest.trees:
  File "/usr/lib64/python2.7/site-packages/obnamlib/fmt_6/repo_tree.py", line 63, in init_forest
    allow_writes=allow_writes)
  File "/usr/lib/python2.7/site-packages/larch/forest.py", line 199, in open_forest
    check_size('key_size', key_size, BadKeySize)
  File "/usr/lib/python2.7/site-packages/larch/forest.py", line 193, in check_size
    if keyname not in ns.get_metadata_keys():
  File "/usr/lib/python2.7/site-packages/larch/nodestore_disk.py", line 167, in get_metadata_keys
    self._load_metadata()
  File "/usr/lib/python2.7/site-packages/larch/nodestore_disk.py", line 148, in _load_metadata
    data = self.journal.cat(self.metadata_name)
  File "/usr/lib/python2.7/site-packages/larch/journal.py", line 162, in cat
    return self.fs.cat(filename)
  File "/usr/lib64/python2.7/site-packages/obnamlib/repo_fs.py", line 58, in cat
    data = self.fs.cat(filename)
  File "/usr/lib64/python2.7/site-packages/obnamlib/plugins/sftp_plugin.py", line 588, in cat
    f.prefetch()
TypeError: prefetch() takes exactly 2 arguments (1 given)


Expected results:

Lock is release and further obnam operations work.

Additional info: