Incorrectly raises ValueError.

[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 891, in receive_data
    for frame in self.incoming_buffer:
  File "/Users/cory/tmp/fuzz-results/env/lib/python2.7/site-packages/h2/frame_buffer.py", line 159, in next
    f.parse_body(memoryview(self.data[9:9+length]))
  File "/Users/cory/tmp/fuzz-results/env/lib/python2.7/site-packages/hyperframe/frame.py", line 463, in parse_body
    raise ValueError()

It would be a lot better if this exception was not a ValueError.

[Lukasa]

Also this one:

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 891, in receive_data
    for frame in self.incoming_buffer:
  File "/Users/cory/tmp/fuzz-results/env/lib/python2.7/site-packages/h2/frame_buffer.py", line 159, in next
    f.parse_body(memoryview(self.data[9:9+length]))
  File "/Users/cory/tmp/fuzz-results/env/lib/python2.7/site-packages/hyperframe/frame.py", line 313, in parse_body
    raise ValueError()
ValueError