glib: Improve error string in VariantTy::new()

Author: sdroege

glib/src/variant_type.rs

@@ -151,7 +151,7 @@ impl VariantTy {
             if ok && end == limit {
                 Ok(&*(type_string.as_bytes() as *const [u8] as *const VariantTy))
             } else {
-                Err(glib_bool_error!("Invalid type {} string", type_string))
+                Err(glib_bool_error!("Invalid type string: '{}'", type_string))
             }
         }
     }