Remove unused kafka.protocol.message bits (#2705)

Author: dpkp

kafka/protocol/message.py

@@ -7,18 +7,6 @@
 from kafka.errors import KafkaTimeoutError
 
 
-MAX_INT = 2 ** 31
-TO_SIGNED = 2 ** 32
-
-def crc32(data):
-    crc = binascii.crc32(data)
-    # CRC is encoded as a signed int in kafka protocol
-    # so we'll convert the unsigned result to signed
-    if crc >= MAX_INT:
-        crc -= TO_SIGNED
-    return crc
-
-
 class Timer:
     __slots__ = ('_start_at', '_expire_at', '_timeout_ms', '_error_message')