Even more helpful error message (use bytes?)

Cython/Compiler/ExprNodes.py

@@ -42,7 +42,7 @@ find_coercion_error = {
     (Builtin.bytes_type, Builtin.str_type) : "Cannot convert 'bytes' object to str implicitly. This is not portable to Py3.",
     (Builtin.str_type, Builtin.unicode_type) : "str objects do not support coercion to unicode, use a unicode string literal instead (u'')",
     (Builtin.str_type, Builtin.bytes_type) : "Cannot convert 'str' to 'bytes' implicitly. This is not portable.",
-    (Builtin.str_type, PyrexTypes.c_char_ptr_type) : "'str' objects do not support coercion to C types.",
+    (Builtin.str_type, PyrexTypes.c_char_ptr_type) : "'str' objects do not support coercion to C types (use 'bytes'?).",
     (PyrexTypes.c_char_ptr_type, Builtin.unicode_type) : "Cannot convert 'char*' to unicode implicitly, decoding required",
     (PyrexTypes.c_uchar_ptr_type, Builtin.unicode_type) : "Cannot convert 'char*' to unicode implicitly, decoding required",
     }.get