bug#64104: Subject: 30.0.50; uncomment-region-default-1

[Stefan Monnier]

>> C-u comment-dwim RET with an active region of the following Python code:
>> 
>> ---
>> # for i in text:
>> #     print("(i): {}".format(str(i)))
>> ---
>> 
>> results in error saying
>> 
>> uncomment-region-default-1: Beginning of buffer

> Stefan, any comments?

- The error we give is not very user-friendly, so it might be good to
  catch it and re-raise it as something more meaning ful the specific
  operation performed.

- I have the vague impression that in some earlier version of that code we
  would not signal an error but just remove as many comment markers as
  possible (but no more than requested).
  That could be a more friendly behavior.


        Stefan