Clean Python Error Handling

Error handling is part of the public behavior. Keep normal flow readable, preserve context, and make recoverable failures explicit.

EH1: Raise Useful Exceptions

Raise exception objects with useful context. Choose built-in exceptions or project-specific subclasses that match the failure.

# Bad
raise Exception("User not found")

# Good
raise UserNotFoundError(f"User not found: {user_id}")

When wrapping an exception, preserve the cause.