¿Pandas json_normalize produce un mensaje confuso de `KeyError`?

Estoy tratando de convertir un JSON anidado en un marco de datos de Pandas. He estado usandojson_normalize con éxito hasta que me encontré con cierto JSON. He hecho una versión más pequeña para recrear el problema.

from pandas.io.json import json_normalize

json=[{"events": [{"schedule": {"date": "2015-08-27",
     "location": {"building": "BDC", "floor": 5},
     "ID": 815},
    "group": "A"},
   {"schedule": {"date": "2015-08-27",
     "location": {"building": "BDC", "floor": 5},
 "ID": 816},
"group": "A"}]}]

Entonces corro:

json_normalize(json[0],'events',[['schedule','date'],['schedule','location','building'],['schedule','location','floor']])

Esperando ver algo como esto:

ID      group   schedule.date   schedule.location.building schedule.location.floor  
'815'   'A'     '2015-08-27'            'BDC'                       5
'816'   'A'     '2015-08-27'            'BDC'                       5

Pero en cambio obtengo este error:

In [2]: json_normalize(json[0],'events',[['schedule','date'],['schedule','location','building'],['schedule','location','floor']])
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-2-b588a9e3ef1d> in <module>()
----> 1 json_normalize(json[0],'events',[['schedule','date'],['schedule','location','building'],['schedule','location','floor']])

/Users/logan/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/pandas/io/json.pyc in json_normalize(data, record_path, meta, meta_prefix, record_prefix)
    739                 records.extend(recs)
    740
--> 741     _recursive_extract(data, record_path, {}, level=0)
    742
    743     result = DataFrame(records)

/Users/logan/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/pandas/io/json.pyc in _recursive_extract(data, path, seen_meta, level)
    734                         meta_val = seen_meta[key]
    735                     else:
--> 736                         meta_val = _pull_field(obj, val[level:])
    737                     meta_vals[key].append(meta_val)
    738

/Users/logan/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/pandas/io/json.pyc in _pull_field(js, spec)
    674         if isinstance(spec, list):
    675             for field in spec:
--> 676                 result = result[field]
    677         else:
    678             result = result[spec]

KeyError: 'schedule'

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