[tests] Remove support for bre-BIP31 ping messages

BIP31 support was added to Bitcoin Core in version 0.6.1. Our test
framework is incompatible with Bitcoin Core versions that old, so remove
all special logic for handling pre-BIP31 pings.

test/functional/test_framework/mininode.py

@@ -37,7 +37,6 @@
 from test_framework.siphash import siphash256
 from test_framework.util import hex_str_to_bytes, bytes_to_hex_str, wait_until
 
-BIP0031_VERSION = 60000
 MY_VERSION = 70014  # past bip-31 for ping/pong
 MY_SUBVERSION = b"/python-mininode-tester:0.0.3/"
 MY_RELAY = 1 # from version 70001 onwards, fRelay should be appended to version messages (BIP37)
@@ -1195,22 +1194,6 @@ def __repr__(self):
         return "msg_getaddr()"
 
 
-class msg_ping_prebip31():
-    command = b"ping"
-
-    def __init__(self):
-        pass
-
-    def deserialize(self, f):
-        pass
-
-    def serialize(self):
-        return b""
-
-    def __repr__(self):
-        return "msg_ping() (pre-bip31)"
-
-
 class msg_ping():
     command = b"ping"
 
@@ -1528,8 +1511,7 @@ def on_inv(self, conn, message):
             conn.send_message(want)
 
     def on_ping(self, conn, message):
-        if conn.ver_send > BIP0031_VERSION:
-            conn.send_message(msg_pong(message.nonce))
+        conn.send_message(msg_pong(message.nonce))
 
     def on_verack(self, conn, message):
         conn.ver_recv = conn.ver_send
@@ -1786,9 +1768,6 @@ def send_message(self, message, pushbuf=False):
             self.last_sent = time.time()
 
     def got_message(self, message):
-        if message.command == b"version":
-            if message.nVersion <= BIP0031_VERSION:
-                self.messagemap[b'ping'] = msg_ping_prebip31
         if self.last_sent + 30 * 60 < time.time():
             self.send_message(self.messagemap[b'ping']())
         self._log_message("receive", message)