Fix unused import warning in isototest error module

isototest/src/errors/util_errors.rs

@@ -1,6 +1,7 @@
 //! This module defines and implements error type which refer to the supporting util of this library.
 //! This means functionality like logging and similar supporting functionality, which do not necessarily
 //! impact the core functionality of this library itself.
+#[cfg(feature = "default-logging")] // HACK: Until other error types implement fmt.
 use std::fmt;
 
 #[derive(Debug)]