Use explicit ValueError when called with incorrect function code (#2089)

pymodbus/datastore/remote.py

@@ -50,12 +50,13 @@ def getValues(self, fc_as_hex, _address, _count=1):
     def setValues(self, fc_as_hex, address, values):
         """Set the datastore with the supplied values."""
         group_fx = self.decode(fc_as_hex)
-        if fc_as_hex in self._write_fc:
-            func_fc = self.__set_callbacks[f"{group_fx}{fc_as_hex}"]
-            if fc_as_hex in {0x0F, 0x10}:
-                self.result = func_fc(address, values)
-            else:
-                self.result = func_fc(address, values[0])
+        if fc_as_hex not in self._write_fc:
+            raise ValueError(f"setValues() called with an non-write function code {fc_as_hex}")
+        func_fc = self.__set_callbacks[f"{group_fx}{fc_as_hex}"]
+        if fc_as_hex in {0x0F, 0x10}:  # Write Multiple Coils, Write Multiple Registers
+            self.result = func_fc(address, values)
+        else:
+            self.result = func_fc(address, values[0])
         if self.result.isError():
             return self.result
         return None