filestream_range_iterator needed a __len()__ method

[1letter]

see: collective/wildcard.media#75

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should the implemented interface changed from

@implementer(IStreamIterator)
class filestream_range_iterator(Iterable):

to

@implementer(IUnboundStreamIterator)
class filestream_range_iterator(Iterable):

because the WSGIResponse Object in Zope.ZPublisher.HTTPResponse check for IUnboundStreamIterator not for IStreamIterator

def setBody(self, body, title='', is_error=False, lock=None):
   # allow locking of the body in the same way as the status
   if self._locked_body:
       return

   if isinstance(body, IOBase):
       body.seek(0, 2)
       length = body.tell()
       body.seek(0)
       self.setHeader('Content-Length', '%d' % length)
       self.body = body
   elif IStreamIterator.providedBy(body):
       self.body = body
       super(WSGIResponse, self).setBody(b'', title, is_error)
   elif IUnboundStreamIterator.providedBy(body):
       self.body = body
       self._streaming = 1
       super(WSGIResponse, self).setBody(b'', title, is_error)
   else:
       super(WSGIResponse, self).setBody(body, title, is_error)

But i'm not so deep in this package, to answer this question.