socketcand: show actual result as well as expectation (#1807)

Author: liamkinne

can/interfaces/socketcand/socketcand.py

@@ -323,7 +323,7 @@ def _expect_msg(self, msg):
         if self.__tcp_tune:
             self.__socket.setsockopt(socket.IPPROTO_TCP, socket.TCP_QUICKACK, 1)
         if not ascii_msg == msg:
-            raise can.CanError(f"{msg} message expected!")
+            raise can.CanError(f"Expected '{msg}' got: '{ascii_msg}'")
 
     def send(self, msg, timeout=None):
         """Transmit a message to the CAN bus.