Catches exception while handling "no space left on device" exception

This bug was originally reported by Holger Levsen (holger@debian.org) in Debian bug #874582:

Package: diffoscope
Version: 78
Severity: minor

hi,

when diffoscope hits ENOSPACE this is excepted, but sadly not really:

$ diffoscope doc/debian-edu-doc_1.923~20170823_amd64.changes debian-edu-doc=
_1.923~20170823_amd64.changes
Traceback (most recent call last):###########################|  100%       =
                      ETA:  0:00:00=20
  File "/usr/lib/python3/dist-packages/diffoscope/comparators/utils/libarch=
ive.py", line 232, in ensure_unpacked
    f.write(block)
OSError: [Errno 28] No space left on device

During handling of the above exception, another exception occurred:

[..]