Because in CliClient.resume() we don't account for the case, when there is an exception in one of the async processing stages:

void resume() {
	...
	try {
		client.startAsync(state -> {
			printer.ifPresent(p -> p.print(state));
			if (!options.shouldSeedAfterDownloaded() && state.getPiecesRemaining() == 0) {
				runtime.shutdown();
			}
		}, 1000); // <-- CompletableFuture.w

Deprecation warning due to invalid escape sequences. Using raw strings or escaping them again helps in resolving this. Check https://github.com/asottile/pyupgrade/ for automatic fix of this.

Syntax warnings are caused due to comparison of literals using is.

Steps to reproduce:

find . -iname '*.py' | grep -Ev 'rdf4|tool|doc' | xargs -P4 -I{} python3.8 -Wall -m py_compile {}
./up