Re: [Bug] "You can't edit this part of the Custom buffer"

[Richard Stallman]

    With the old behavior, when you try to insert something in a Customize
    buffer, you get an error:

      "Text is read-only: Attempt to change text outside editable field"

    Now, you get the error:

      "You can't edit this part of the Custom buffer"

That was the aim of my change.  It worked right with editable fields,
but failed with buttons because they don't have their own keymaps.  I
fixed it.

Should buttons work by having their own keymaps?  It seems cleaner
in principle.