cache miss raises KeyError

[romanchyla]

as part of the old ClaimsRecorder (still valid for the new code)

ERROR   21497 [05/19/2017 19:19:36]:    Unrecoverable exception: (u'2004SPIE.5487..211C', <object object at 0x7f3a50fe22a0>, 'search_identifiers', True) (Traceback (most recent call last):
  File "/app/ADSOrcid/pipeline/GenericWorker.py", line 210, in on_message
    header_frame=header_frame)
  File "/app/ADSOrcid/pipeline/ClaimsRecorder.py", line 36, in process_payload
    rec = updater.retrieve_record(bibcode)
  File "/app/ADSOrcid/updater.py", line 71, in retrieve_record
    metadata = retrieve_metadata(bibcode)
  File "/usr/local/lib/python2.7/dist-packages/cachetools/__init__.py", line 52, in wrapper
    cache[k] = v
  File "/usr/local/lib/python2.7/dist-packages/cachetools/ttl.py", line 125, in __setitem__
    cache_setitem(self, key, value)
  File "/usr/local/lib/python2.7/dist-packages/cachetools/cache.py", line 51, in __setitem__
    self.popitem()
  File "/usr/local/lib/python2.7/dist-packages/cachetools/ttl.py", line 241, in popitem
    return (key, self.pop(key))
  File "/usr/local/lib/python2.7/dist-packages/cachetools/ttl.py", line 248, in wrapper
    return method(self, *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/cachetools/cache.py", line 117, in pop
    raise KeyError(key)
KeyError: (u'2004SPIE.5487..211C', <object object at 0x7f3a50fe22a0>, 'search_identifiers', True)
)
ERROR   21497 [05/19/2017 19:19:50]:    Unrecoverable exception: (u'2004SPIE.5487..211C', <object object at 0x7f3a50fe22a0>, 'search_identifiers', True) (Traceback (most recent call last):
  File "/app/ADSOrcid/pipeline/GenericWorker.py", line 210, in on_message
    header_frame=header_frame)
  File "/app/ADSOrcid/pipeline/ClaimsRecorder.py", line 36, in process_payload
    rec = updater.retrieve_record(bibcode)
  File "/app/ADSOrcid/updater.py", line 71, in retrieve_record
    metadata = retrieve_metadata(bibcode)
  File "/usr/local/lib/python2.7/dist-packages/cachetools/__init__.py", line 52, in wrapper
    cache[k] = v
  File "/usr/local/lib/python2.7/dist-packages/cachetools/ttl.py", line 125, in __setitem__
    cache_setitem(self, key, value)
  File "/usr/local/lib/python2.7/dist-packages/cachetools/cache.py", line 51, in __setitem__
    self.popitem()
  File "/usr/local/lib/python2.7/dist-packages/cachetools/ttl.py", line 241, in popitem
    return (key, self.pop(key))
  File "/usr/local/lib/python2.7/dist-packages/cachetools/ttl.py", line 248, in wrapper
    return method(self, *args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/cachetools/cache.py", line 117, in pop
    raise KeyError(key)
KeyError: (u'2004SPIE.5487..211C', <object object at 0x7f3a50fe22a0>, 'search_identifiers', True)
)