Also mention regular abi.encode in error message.

libsolidity/analysis/TypeChecker.cpp

@@ -1797,7 +1797,10 @@ bool TypeChecker::visit(FunctionCall const& _functionCall)
 			functionType->kind() == FunctionType::Kind::SHA256 ||
 			functionType->kind() == FunctionType::Kind::RIPEMD160
 		)
-			msg += " This function requires a single bytes argument. Use abi.encodePacked(...) to properly encode the values.";
+			msg +=
+				" This function requires a single bytes argument."
+				" Use abi.encodePacked(...) to obtain the pre-0.5.0 behaviour"
+				" or abi.encode(...) to use ABI encoding.";
 		m_errorReporter.typeError(_functionCall.location(), msg);
 	}
 	else if (isPositionalCall)
@@ -1853,7 +1856,10 @@ bool TypeChecker::visit(FunctionCall const& _functionCall)
 					functionType->kind() == FunctionType::Kind::SHA256 ||
 					functionType->kind() == FunctionType::Kind::RIPEMD160
 				)
-					msg += " This function requires a single bytes argument. Use abi.encodePacked(...) to properly encode the values.";
+					msg +=
+						" This function requires a single bytes argument."
+						" Use abi.encodePacked(...) to obtain the pre-0.5.0 behaviour"
+						" or abi.encode(...) to use ABI encoding.";
 				m_errorReporter.typeError(arguments[i]->location(), msg);
 			}
 		}

test/libsolidity/syntaxTests/globalFunctions/keccak256_with_wrong_arg_count.sol

@@ -6,6 +6,6 @@ contract C {
     }
 }
 // ----
-// TypeError: (55-66): Wrong argument count for function call: 0 arguments given but expected 1. This function requires a single bytes argument. Use abi.encodePacked(...) to properly encode the values.
+// TypeError: (55-66): Wrong argument count for function call: 0 arguments given but expected 1. This function requires a single bytes argument. Use abi.encodePacked(...) to obtain the pre-0.5.0 behaviour or abi.encode(...) to use ABI encoding.
-// TypeError: (100-107): Invalid type for argument in function call. Invalid implicit conversion from uint256 to bytes memory requested. This function requires a single bytes argument. Use abi.encodePacked(...) to properly encode the values.
+// TypeError: (100-107): Invalid type for argument in function call. Invalid implicit conversion from uint256 to bytes memory requested. This function requires a single bytes argument. Use abi.encodePacked(...) to obtain the pre-0.5.0 behaviour or abi.encode(...) to use ABI encoding.
-// TypeError: (132-159): Wrong argument count for function call: 2 arguments given but expected 1. This function requires a single bytes argument. Use abi.encodePacked(...) to properly encode the values.
+// TypeError: (132-159): Wrong argument count for function call: 2 arguments given but expected 1. This function requires a single bytes argument. Use abi.encodePacked(...) to obtain the pre-0.5.0 behaviour or abi.encode(...) to use ABI encoding.

test/libsolidity/syntaxTests/globalFunctions/ripemd160_with_wrong_arg_count.sol

@@ -6,6 +6,6 @@ contract C {
     }
 }
 // ----
-// TypeError: (55-66): Wrong argument count for function call: 0 arguments given but expected 1. This function requires a single bytes argument. Use abi.encodePacked(...) to properly encode the values.
+// TypeError: (55-66): Wrong argument count for function call: 0 arguments given but expected 1. This function requires a single bytes argument. Use abi.encodePacked(...) to obtain the pre-0.5.0 behaviour or abi.encode(...) to use ABI encoding.
-// TypeError: (100-107): Invalid type for argument in function call. Invalid implicit conversion from uint256 to bytes memory requested. This function requires a single bytes argument. Use abi.encodePacked(...) to properly encode the values.
+// TypeError: (100-107): Invalid type for argument in function call. Invalid implicit conversion from uint256 to bytes memory requested. This function requires a single bytes argument. Use abi.encodePacked(...) to obtain the pre-0.5.0 behaviour or abi.encode(...) to use ABI encoding.
-// TypeError: (132-159): Wrong argument count for function call: 2 arguments given but expected 1. This function requires a single bytes argument. Use abi.encodePacked(...) to properly encode the values.
+// TypeError: (132-159): Wrong argument count for function call: 2 arguments given but expected 1. This function requires a single bytes argument. Use abi.encodePacked(...) to obtain the pre-0.5.0 behaviour or abi.encode(...) to use ABI encoding.

test/libsolidity/syntaxTests/globalFunctions/sha256_with_wrong_arg_count.sol

@@ -6,6 +6,6 @@ contract C {
     }
 }
 // ----
-// TypeError: (55-63): Wrong argument count for function call: 0 arguments given but expected 1. This function requires a single bytes argument. Use abi.encodePacked(...) to properly encode the values.
+// TypeError: (55-63): Wrong argument count for function call: 0 arguments given but expected 1. This function requires a single bytes argument. Use abi.encodePacked(...) to obtain the pre-0.5.0 behaviour or abi.encode(...) to use ABI encoding.
-// TypeError: (94-101): Invalid type for argument in function call. Invalid implicit conversion from uint256 to bytes memory requested. This function requires a single bytes argument. Use abi.encodePacked(...) to properly encode the values.
+// TypeError: (94-101): Invalid type for argument in function call. Invalid implicit conversion from uint256 to bytes memory requested. This function requires a single bytes argument. Use abi.encodePacked(...) to obtain the pre-0.5.0 behaviour or abi.encode(...) to use ABI encoding.
-// TypeError: (126-150): Wrong argument count for function call: 2 arguments given but expected 1. This function requires a single bytes argument. Use abi.encodePacked(...) to properly encode the values.
+// TypeError: (126-150): Wrong argument count for function call: 2 arguments given but expected 1. This function requires a single bytes argument. Use abi.encodePacked(...) to obtain the pre-0.5.0 behaviour or abi.encode(...) to use ABI encoding.

test/libsolidity/syntaxTests/specialFunctions/single_non_bytes_arg.sol

@@ -7,6 +7,6 @@ contract C {
     function g(bytes32) pure internal {}
 }
 // ----
-// TypeError: (64-71): Invalid type for argument in function call. Invalid implicit conversion from uint256 to bytes memory requested. This function requires a single bytes argument. Use abi.encodePacked(...) to properly encode the values.
+// TypeError: (64-71): Invalid type for argument in function call. Invalid implicit conversion from uint256 to bytes memory requested. This function requires a single bytes argument. Use abi.encodePacked(...) to obtain the pre-0.5.0 behaviour or abi.encode(...) to use ABI encoding.
-// TypeError: (92-99): Invalid type for argument in function call. Invalid implicit conversion from uint256 to bytes memory requested. This function requires a single bytes argument. Use abi.encodePacked(...) to properly encode the values.
+// TypeError: (92-99): Invalid type for argument in function call. Invalid implicit conversion from uint256 to bytes memory requested. This function requires a single bytes argument. Use abi.encodePacked(...) to obtain the pre-0.5.0 behaviour or abi.encode(...) to use ABI encoding.
-// TypeError: (123-130): Invalid type for argument in function call. Invalid implicit conversion from uint256 to bytes memory requested. This function requires a single bytes argument. Use abi.encodePacked(...) to properly encode the values.
+// TypeError: (123-130): Invalid type for argument in function call. Invalid implicit conversion from uint256 to bytes memory requested. This function requires a single bytes argument. Use abi.encodePacked(...) to obtain the pre-0.5.0 behaviour or abi.encode(...) to use ABI encoding.