message: [logger] fix warning.
diff: @@ -9,7 +9,6 @@ use log4rs::config::{Appender, Config, Root};
  use log4rs::encode::pattern::PatternEncoder;
  use log4rs::Handle;
  use std::cell::RefCell;
  -use std::error::Error;
  use std::path::PathBuf;
  use std::sync::Once;
  @@ -151,7 +150,7 @@ pub fn init_with_default_level(default_level: &str) -> LoggerHandle {
  build_config(LoggerConfigArg::new(true, level, None)).expect("build log config fail.");
  let handle = match log4rs::init_config(config) {
  Ok(handle) => handle,
  - Err(e) => panic!(format!("{}", e.description())),
  + Err(e) => panic!(format!("{}", e.to_string())),
  };
  LoggerHandle::new(true, level, None, handle)
  }
  