If this option is not used or used with zero value, if MAGIC does
not match :macro:`NGHTTP2_CLIENT_MAGIC`, `nghttp2_session_recv()`
and `nghttp2_session_mem_recv()` will return error
- :macro:`NGHTTP2_ERR_BAD_CLIENT_MAGIC`, which is fatal error.
+ :macro:`nghttp2_error.NGHTTP2_ERR_BAD_CLIENT_MAGIC`, which is fatal
+ error.