Where is this extern crate defined?

On rtsp-rs/client.rs at master · sgodwincs/rtsp-rs · GitHub, it says

extern crate rtsp;

but I get

error[E0463]: can't find crate for `rtsp`
 --> rtsp-2/tests/connection_shutdown_tests.rs:3:1
3 | extern crate rtsp;
  | ^^^^^^^^^^^^^^^^^^ can't find crate

On the Cargo.toml there's no rtsp crate: rtsp-rs/Cargo.toml at master · sgodwincs/rtsp-rs · GitHub

Is this an error or am I missing something?

According to https://stackoverflow.com/a/54378840/5884503 I don't need extern crate anymore because of the things in Cargo.toml but there's no rtsp crate there

This is an error; @lucaszanella filed an issue for it recently. It looks like that test should be using rtsp_2 instead, and you're right that no extern crate is needed.