Borg fails to create new backups ("archives") with python-msgpack later
than 0.4.6:

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Traceback (most recent call last):
  File "/gnu/store/14v77f8h72z5qvzl74m5rv0pkkrk1l5s-borg-1.1.4/bin/.borg-real", line 6, in <module>
    from pkg_resources import load_entry_point
  File "/gnu/store/3lkypf5wnsnvkaidhw0pv7k3yjfh1r9g-python-3.6.3/lib/python3.6/site-packages/pkg_resources/__init__.py", line 3017, in <module>
    @_call_aside
  File "/gnu/store/3lkypf5wnsnvkaidhw0pv7k3yjfh1r9g-python-3.6.3/lib/python3.6/site-packages/pkg_resources/__init__.py", line 3003, in _call_aside
    f(*args, **kwargs)
  File "/gnu/store/3lkypf5wnsnvkaidhw0pv7k3yjfh1r9g-python-3.6.3/lib/python3.6/site-packages/pkg_resources/__init__.py", line 3030, in _initialize_master_working_set
    working_set = WorkingSet._build_master()
  File "/gnu/store/3lkypf5wnsnvkaidhw0pv7k3yjfh1r9g-python-3.6.3/lib/python3.6/site-packages/pkg_resources/__init__.py", line 659, in _build_master
    ws.require(__requires__)
  File "/gnu/store/3lkypf5wnsnvkaidhw0pv7k3yjfh1r9g-python-3.6.3/lib/python3.6/site-packages/pkg_resources/__init__.py", line 967, in require
    needed = self.resolve(parse_requirements(requirements))
  File "/gnu/store/3lkypf5wnsnvkaidhw0pv7k3yjfh1r9g-python-3.6.3/lib/python3.6/site-packages/pkg_resources/__init__.py", line 853, in resolve
    raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'msgpack-python>=0.4.6' distribution was not found and is required by borgbackup
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I'll create a python-msgpack-0.4.6 package as a quick fix as soon as I
get a bug number from debbugs.