message: Fix error messages in tests
diff: @@ -56,7 +56,7 @@ mod test {
  assert_eq!(minuend, "123");
  assert_eq!(subtrahend, "456");
  }
  - _ => panic!("expect underflow error"),
  + _ => panic!("expect different error"),
  }
  }
  @@ -72,7 +72,7 @@ mod test {
  assert_eq!(minuend, "777");
  assert_eq!(subtrahend, "1234");
  }
  - _ => panic!("expect underflow error"),
  + _ => panic!("expect different error"),
  }
  }
  @@ -81,7 +81,7 @@ mod test {
  let error: StdError = unauthorized();
  match error {
  StdError::Unauthorized { .. } => {}
  - _ => panic!("expect underflow error"),
  + _ => panic!("expect different error"),
  }
  }
  }
  