Unexpected IndexError

[Lukasa]

Encountered the following traceback while fuzzing hyper-h2:

Traceback (most recent call last):
  File "script.py", line 10, in <module>
    c.receive_data(sys.stdin.read())
  File "/Users/cory/tmp/fuzz-results/env/lib/python2.7/site-packages/h2/connection.py", line 892, in receive_data
    events.extend(self._receive_frame(frame))
  File "/Users/cory/tmp/fuzz-results/env/lib/python2.7/site-packages/h2/connection.py", line 915, in _receive_frame
    frames, events = self._frame_dispatch_table[frame.__class__](frame)
  File "/Users/cory/tmp/fuzz-results/env/lib/python2.7/site-packages/h2/connection.py", line 956, in _receive_headers_frame
    headers = self.decoder.decode(frame.data)
  File "/Users/cory/tmp/fuzz-results/env/lib/python2.7/site-packages/hpack/hpack.py", line 334, in decode
    data[current_index:]
  File "/Users/cory/tmp/fuzz-results/env/lib/python2.7/site-packages/hpack/hpack.py", line 375, in _decode_literal_index
    return self._decode_literal(data, True)
  File "/Users/cory/tmp/fuzz-results/env/lib/python2.7/site-packages/hpack/hpack.py", line 416, in _decode_literal
    length, consumed = decode_integer(data, 7)
  File "/Users/cory/tmp/fuzz-results/env/lib/python2.7/site-packages/hpack/hpack.py", line 60, in decode_integer
    number = to_byte(data[index]) & mask
IndexError: string index out of range

It would be good if this threw a hpack-specific exception instead of IndexError.