message: Fix macro expansion issue failing future compatibility check.
diff: @@ -665,7 +665,9 @@ impl Client {
  return Err(Error::new(ErrorKind::Other, msg));
  }
  - ServerOp::Unknown(line) => log::warn!("unknown op: {}", line),
  + ServerOp::Unknown(line) => {
  + log::warn!("unknown op: {}", line);
  + }
  }
  }
  