bug#40388: Calibre test suite fails

[Josh Holland <josh@inv.alid.pw>]

Hi,

Both on my local machine and on the CI[0], the Calibre test suite has
been failing with the following error:

======================================================================
ERROR: test_msgpack (calibre.test_build.BuildTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/tmp/guix-build-calibre-3.42.0.drv-0/calibre-3.42.0/src/calibre/test_build.py", line 124, in test_msgpack
    self.assertEqual(obj, msgpack_loads(s))
  File "/tmp/guix-build-calibre-3.42.0.drv-0/calibre-3.42.0/src/calibre/utils/serialize.py", line 113, in msgpack_loads
    return msgpack.unpackb(dump, ext_hook=msgpack_decoder, raw=False, use_list=use_list)
  File "/gnu/store/z7dz4iiaivmadhk0x50qs5zv3rwykrmd-python2-msgpack-1.0.0/lib/python2.7/site-packages/msgpack/fallback.py", line 129, in unpackb
    ret = unpacker._unpack()
  File "/gnu/store/z7dz4iiaivmadhk0x50qs5zv3rwykrmd-python2-msgpack-1.0.0/lib/python2.7/site-packages/msgpack/fallback.py", line 666, in _unpack
    "%s is not allowed for map key" % str(type(key))
ValueError: <type 'int'> is not allowed for map key

----------------------------------------------------------------------

This is happening on both staging and master.  There have been no
changes to the calibre package itself since January.  I have run a git
bisect and the offending change appears to be in commit
66ab2f5e3a0df665f6e39203aedd2bf4812e6a71, when python-msgpack was
updated to version 1.0.0.

[0]: e.g. http://ci.guix.gnu.org/build/2485977/details

--
Josh Holland