Description of problem:
When running a kickstart installation and the installation source is set to Red Hat CDN using the rhsm kickstart command and the command fails anaconda prompts an error asking user if he wants to continue, when selecting "NO" anaconda ends in traceback, offers user to report a bug and in case of graphical installation the installation starts in the background.

Version-Release number of selected component (if applicable):
anaconda-33.16.7.5-1.el8

How reproducible:
Always

Steps to Reproduce:
1.run a kickstart installation containing the following line:
rhsm --organization=unknown_organization --activation-key=unknown_key

2. when prompted with an error and asked if you want to continue click "NO"

Actual results:
Anaconda tracebacks:
Traceback (most recent call first):
File "/usr/lib64/python3.6/site-packages/pyanaconda/ui/lib/subscription.py", line 124, in kickstart_error_handler
raise exn
File "/usr/lib64/python3.6/site-packages/pyanaconda/ui/lib/subscription.py", line 297, in register_and_subscribe
error_callback(str(e))
File "/usr/lib64/python3.6/threading.py", line 885, in run
self._target(*self._args, **self._kwargs)
File "/usr/lib64/python3.6/site-packages/pyanaconda/threading.py", line 280, in run
threading.Thread.run(self)
pyanaconda.ui.lib.subscription.KickstartRegistrationError: Organization unknown_organization does not exist.

In case of graphical installation the installation starts in the background

Expected results:
Anaconda gracefully exits