[tests] Explicitly disallow support for p2p versions below 60001

The mininode module includes code to support p2p versions below
60001. However, the test_framework does not support versions
of Bitcoin Core before V0.13.0. Remove code supporting
p2p versions before 60001 (which has never been run).

test/functional/test_framework/mininode.py

@@ -37,6 +37,7 @@ from threading import RLock, Thread
 from test_framework.siphash import siphash256
 from test_framework.util import hex_str_to_bytes, bytes_to_hex_str, wait_until
 
+MIN_VERSION_SUPPORTED = 60001
 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)
@@ -1423,11 +1424,8 @@ class NodeConnCB():
         self.verack_received = True
 
     def on_version(self, conn, message):
-        if message.nVersion >= 209:
-            conn.send_message(msg_verack())
-        conn.ver_send = min(MY_VERSION, message.nVersion)
-        if message.nVersion < 209:
-            conn.ver_recv = conn.ver_send
+        assert message.nVersion >= MIN_VERSION_SUPPORTED, "Version {} received. Test framework only supports versions greater than {}".format(message.nVersion, MIN_VERSION_SUPPORTED)
+        conn.send_message(msg_verack())
         conn.nServices = message.nServices
 
     # Connection helper methods
@@ -1609,40 +1607,27 @@ class NodeConn(asyncore.dispatcher):
                     return
                 if self.recvbuf[:4] != self.MAGIC_BYTES[self.network]:
                     raise ValueError("got garbage %s" % repr(self.recvbuf))
-                if self.ver_recv < 209:
-                    if len(self.recvbuf) < 4 + 12 + 4:
-                        return
-                    command = self.recvbuf[4:4+12].split(b"\x00", 1)[0]
-                    msglen = struct.unpack("<i", self.recvbuf[4+12:4+12+4])[0]
-                    checksum = None
-                    if len(self.recvbuf) < 4 + 12 + 4 + msglen:
-                        return
-                    msg = self.recvbuf[4+12+4:4+12+4+msglen]
-                    self.recvbuf = self.recvbuf[4+12+4+msglen:]
-                else:
-                    if len(self.recvbuf) < 4 + 12 + 4 + 4:
-                        return
-                    command = self.recvbuf[4:4+12].split(b"\x00", 1)[0]
-                    msglen = struct.unpack("<i", self.recvbuf[4+12:4+12+4])[0]
-                    checksum = self.recvbuf[4+12+4:4+12+4+4]
-                    if len(self.recvbuf) < 4 + 12 + 4 + 4 + msglen:
-                        return
-                    msg = self.recvbuf[4+12+4+4:4+12+4+4+msglen]
-                    th = sha256(msg)
-                    h = sha256(th)
-                    if checksum != h[:4]:
-                        raise ValueError("got bad checksum " + repr(self.recvbuf))
-                    self.recvbuf = self.recvbuf[4+12+4+4+msglen:]
-                if command in self.messagemap:
-                    f = BytesIO(msg)
-                    t = self.messagemap[command]()
-                    t.deserialize(f)
-                    self.got_message(t)
-                else:
-                    logger.warning("Received unknown command from %s:%d: '%s' %s" % (self.dstaddr, self.dstport, command, repr(msg)))
-                    raise ValueError("Unknown command: '%s'" % (command))
+                if len(self.recvbuf) < 4 + 12 + 4 + 4:
+                    return
+                command = self.recvbuf[4:4+12].split(b"\x00", 1)[0]
+                msglen = struct.unpack("<i", self.recvbuf[4+12:4+12+4])[0]
+                checksum = self.recvbuf[4+12+4:4+12+4+4]
+                if len(self.recvbuf) < 4 + 12 + 4 + 4 + msglen:
+                    return
+                msg = self.recvbuf[4+12+4+4:4+12+4+4+msglen]
+                th = sha256(msg)
+                h = sha256(th)
+                if checksum != h[:4]:
+                    raise ValueError("got bad checksum " + repr(self.recvbuf))
+                self.recvbuf = self.recvbuf[4+12+4+4+msglen:]
+                if command not in self.messagemap:
+                    raise ValueError("Received unknown command from %s:%d: '%s' %s" % (self.dstaddr, self.dstport, command, repr(msg)))
+                f = BytesIO(msg)
+                t = self.messagemap[command]()
+                t.deserialize(f)
+                self.got_message(t)
         except Exception as e:
-            logger.exception('got_data:', repr(e))
+            logger.exception('Error reading message:', repr(e))
             raise
 
     def send_message(self, message, pushbuf=False):
@@ -1655,10 +1640,9 @@ class NodeConn(asyncore.dispatcher):
         tmsg += command
         tmsg += b"\x00" * (12 - len(command))
         tmsg += struct.pack("<I", len(data))
-        if self.ver_send >= 209:
-            th = sha256(data)
-            h = sha256(th)
-            tmsg += h[:4]
+        th = sha256(data)
+        h = sha256(th)
+        tmsg += h[:4]
         tmsg += data
         with mininode_lock:
             if (len(self.sendbuf) == 0 and not pushbuf):