message: Fix typo in test code
diff: @@ -829,7 +829,7 @@ mod test {
  SystemResult::Err(SystemError::InvalidRequest { request: err, .. }) => {
  assert_eq!(err.as_slice(), request)
  }
  - SystemResult::Err(error) => panic!("Unexpeted error: {:?}", error),
  + SystemResult::Err(err) => panic!("Unexpected error: {:?}", err),
  }
  }
  @@ -857,7 +857,7 @@ mod test {
  SystemResult::Err(SystemError::NoSuchContract { addr }) => {
  assert_eq!(addr, HumanAddr::from("non-existent"))
  }
  - SystemResult::Err(error) => panic!("Unexpeted error: {:?}", error),
  + SystemResult::Err(err) => panic!("Unexpected error: {:?}", err),
  }
  }
  