message: fix error match
diff: @@ -526,7 +526,7 @@ impl IndexWriter {
  let indexing_worker_result =
  worker_handle
  .join()
  - .map_err(|e| Error::from(ErrorKind::ErrorInThread(format!("{:?}", e))))?;
  + .map_err(|e| Error::from_kind(ErrorKind::ErrorInThread(format!("{:?}", e))))?;
  indexing_worker_result?;
  // add a new worker for the next generation.
  @@ -601,7 +601,7 @@ mod tests {
  use schema::{self, Document};
  use Index;
  use Term;
  - use Error;
  + use error::*;
  use env_logger;
  #[test]
  @@ -610,7 +610,7 @@ mod tests {
  let index = Index::create_in_ram(schema_builder.build());
  let _index_writer = index.writer(40_000_000).unwrap();
  match index.writer(40_000_000) {
  - Err(Error::FileAlreadyExists(_)) => {}
  + Err(Error(ErrorKind::FileAlreadyExists(_), _)) => {}
  _ => panic!("Expected FileAlreadyExists error"),
  }
  }
  