events: fix variant panic message

src/events.rs

@@ -28,7 +28,7 @@ macro_rules! impl_variant_type {
             fn into(self) -> $type {
                 match self {
                     Variant::$var_type(value) => value,
-                    _ => panic!("Expected Variant::$var_type, but got {:?}", self)
+                    _ => panic!(concat!("Expected Variant::", stringify!($var_type), "but got {:?}"), self)
                 }
             }
         }