Bug: startup hangs when cannot read nats credentials

[swelborn]

Describe the bug When supplying user credentials that cannot be read by the user, faststream attempts to start but does not fail with a "permission denied" like underlying nats-py does.

How to reproduce https://github.com/swelborn/nats-creds-reproducer/tree/main

Expected behavior Failure if we cannot read the credentials, rather than hanging

Observed behavior Not failing.

Environment Reproducer above uses uv for environment (using uv run --with ...