ref(rules): Raise exception on keyerror

[ceorourke]

Follow up from #70831 (comment) to make this raise an exception rather than just log an error.

[saponifi3d]

TIL that this will also automatically use the exception. 🔥

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 80.01%. Comparing base (1f61c87) to head (51592d6).
Report is 13 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #70880       +/-   ##
===========================================
+ Coverage   63.16%   80.01%   +16.84%     
===========================================
  Files        6501     6506        +5     
  Lines      290600   290891      +291     
  Branches    50105    50133       +28     
===========================================
+ Hits       183554   232743    +49189     
+ Misses     106606    57714    -48892     
+ Partials      440      434        -6     

Files	Coverage Δ
src/sentry/buffer/redis.py	92.05% <0.00%> (+60.03%)	⬆️

... and 1776 files with indirect coverage changes

[gmisiolek-sbm]

After this change there are errors:

worker-1                                        | Traceback (most recent call last):
worker-1                                        |   File "/usr/local/lib/python3.11/site-packages/sentry/buffer/redis.py", line 74, in callback
worker-1                                        |     callback = self._registry[buffer_hook_event]
worker-1                                        |                ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^
worker-1                                        | KeyError: <BufferHookEvent.FLUSH: 'flush'>
worker-1                                        | 22:11:00 [ERROR] sentry.buffer.redis: buffer_hook_event.missing
worker-1                                        | Traceback (most recent call last):
worker-1                                        |   File "/usr/local/lib/python3.11/site-packages/sentry/buffer/redis.py", line 313, in process_batch
worker-1                                        |     redis_buffer_registry.callback(BufferHookEvent.FLUSH, self)
worker-1                                        |   File "/usr/local/lib/python3.11/site-packages/sentry/buffer/redis.py", line 78, in callback
worker-1                                        |     return callback(data)
worker-1                                        |            ^^^^^^^^
worker-1                                        | UnboundLocalError: cannot access local variable 'callback' where it is not associated with a value

why return has been removed?