Allow repr(ModbusException) to return complete information (#1779)

pymodbus/exceptions.py

@@ -24,7 +24,7 @@ def __init__(self, string):
         :param string: The message to append to the error
         """
         self.string = string
-        super().__init__()
+        super().__init__(string)
 
     def __str__(self):
         """Return string representation."""