Clarify error message.

Cython/Compiler/Nodes.py

@@ -747,7 +747,7 @@ class CFuncDeclaratorNode(CDeclaratorNode):
                             and not (exc_val_type == PyrexTypes.c_char_type
                                      and self.exception_value.value == '*')):
                         error(self.exception_value.pos,
-                              "Exception value must be a Python exception or cdef function with no arguments or *.")
+                              "Exception value must be a Python exception, or C++ function with no arguments, or *.")
                     exc_val = self.exception_value
                 else:
                     self.exception_value = self.exception_value.analyse_types(env).coerce_to(