Calibre will no longer start

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Calibre previously started fine, now it fails to start with the following message:

steve@rosie ~]$ calibre
Traceback (most recent call last):
  File "/usr/bin/calibre", line 19, in <module>
    from calibre.gui_launch import calibre
  File "/usr/lib64/calibre/calibre/__init__.py", line 28, in <module>
    from calibre.startup import winutil, winutilerror
  File "/usr/lib64/calibre/calibre/startup.py", line 93, in <module>
    set_translators()
  File "/usr/lib64/calibre/calibre/utils/localization.py", line 208, in set_translators
    mpath = get_lc_messages_path(lang)
  File "/usr/lib64/calibre/calibre/utils/localization.py", line 107, in get_lc_messages_path
    if lang in available_translations():
  File "/usr/lib64/calibre/calibre/utils/localization.py", line 21, in available_translations
    stats = msgpack_loads(open(stats, 'rb').read())
  File "/usr/lib64/calibre/calibre/utils/serialize.py", line 108, in msgpack_loads
    return msgpack.unpackb(dump, ext_hook=msgpack_decoder, raw=False)
  File "msgpack/_unpacker.pyx", line 100, in msgpack._unpacker.unpackb (msgpack/_unpacker.cpp:102)
TypeError: unpackb() got an unexpected keyword argument 'raw'
/usr/lib64/calibre/calibre/ptempfile.py:29: RuntimeWarning: Parent module 'calibre' not found while handling absolute import
  import shutil

This is a problem with msgpack, but I have the most up-to-date msgpack installed (0.5.6).