stefanv/ipython — comment on commit 2ac6267c3ace0f0f64aa3e10379028bda24cdd52
File: IPython/lib/security.py line 49
By fperez:

No, not an exception, just an error message to stderr: exceptions are useful for programmatic use, but they are not very user friendly. Alternatively, you can import `from IPython.core.error import UsageError`. That error is a real exception (in case this code is used by something else) but we special-case it and don't show a traceback, for situations like this.