Added echo script

tests/echo.py

@@ -0,0 +1,24 @@
+#!/usr/bin/env python3
+
+import os
+import sys
+import time
+
+sys.path.append(os.path.join(os.path.dirname(os.path.realpath(__file__)), ".."))
+from panda import Panda
+
+# This script is intended to be used in conjunction with the echo_loopback_test.py test script from panda jungle.
+# It sends a reversed response back for every message received containing b"test".
+
+# Resend every CAN message that has been received on the same bus, but with the data reversed
+if __name__ == "__main__":
+  p = Panda()
+  p.set_safety_mode(Panda.SAFETY_ALLOUTPUT)
+  while True:
+    incoming = p.can_recv()
+    for message in incoming:
+      address, notused, data, bus = message
+      if b'test' in data:
+        p.can_send(address, data[::-1], bus)
+
+