HostedFiles: calling non existing methods raises ValueError instead of AttributeError

All other subclasses of 'Resource' raise an AttributeError when calling methods/attributes which are not existing, but HostedFile does not, it raises a ValueError:

In [36]: a = b.attachments[0]

In [37]: a.data.boo
---------------------------------------------------------------------------
<type 'exceptions.ValueError'> Traceback (most recent call last)

/media/disk-1/launchpad-vfs/trunk/<ipython console> in <module>()

/media/disk-1/lp_api/launnchpadlib/trunk/launchpadlib/resource.py in __getattr__(self, attr)
    281 """Try to retrive a named operation or parameter of the given name."""
    282 try:
--> 283 return self.lp_get_parameter(attr)
    284 except KeyError:
    285 pass

/media/disk-1/lp_api/launnchpadlib/trunk/launchpadlib/resource.py in lp_get_parameter(self, param_name)
    183 representation, if the parameter is a link.
    184 """
--> 185 self._ensure_representation()
    186 for suffix in ['_link', '_collection_link']:
    187 param = self._wadl_resource.get_parameter(

/media/disk-1/lp_api/launnchpadlib/trunk/launchpadlib/resource.py in _ensure_representation(self)
    304 representation = self._root._browser.get(self._wadl_resource)
    305 self.__dict__['_wadl_resource'] = self._wadl_resource.bind(
--> 306 representation, self.JSON_MEDIA_TYPE)
    307
    308

/media/disk-1/lp_api/launnchpadlib/trunk/launchpadlib/wadllib/application.py in bind(self, representation, media_type, representation_needs_processing, representation_definition)
    324 representation, media_type,
    325 representation_needs_processing,
--> 326 representation_definition)
    327
    328 def get_representation_definition(self, media_type):

/media/disk-1/lp_api/launnchpadlib/trunk/launchpadlib/wadllib/application.py in __init__(self, application, url, resource_type, representation, media_type, representation_needs_processing, representation_definition)
    261 if media_type == 'application/json':
    262 if representation_needs_processing:
--> 263 self.representation = simplejson.loads(representation)
    264 else:
    265 self.representation = representation

/media/disk-1/launchpad-vfs/trunk/build/bdist.linux-x86_64/egg/simplejson/__init__.py in loads(s, encoding, cls, object_hook, **kw)

/media/disk-1/launchpad-vfs/trunk/build/bdist.linux-x86_64/egg/simplejson/decoder.py in decode(self, s, _w)

/media/disk-1/launchpad-vfs/trunk/build/bdist.linux-x86_64/egg/simplejson/decoder.py in raw_decode(self, s, **kw)

<type 'exceptions.ValueError'>: No JSON object could be decoded

In [38]: