dht

Creating a new issue based on lbryio/lbry-sdk#877

• Update ensure_directory_exists() to check that the directory is writable by the current process.
• If it's not, return a useful error
• Add tests to cover the case when
  • download directory does not exist
  • download dir exists but is not writable
  • dir exists an

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

Simple mistakes trigger unclear error messages in the ALBERT example, that is:

• Absence of the unpacked data for trainer (currently triggers requests.exceptions.HTTPError: 404 Client Error: Not Found for url: https://huggingface.co/api/models/data/tokenizer)
• Running all peers in --client_mode (currently triggers AllReduce failed: could not find a group)

It would be great to

right now the debug log level is unusable, too much of it is spamming the logs, we need to downgrade the less informative ones to trace level.