assert message linefeed

["John Belmonte" <jvb@...>]

I'd like to suggest that assert add a linefeed to the message string for us.
In the case of disabled traceback, lack of a linefeed leaves a "hanging"
command line.  Try running this as a script:

  _ERRORMESSAGE = _ALERT
  assert(nil, "oh boy")

Of course other solutions are to always have an explicit linefeed, or to
redefine assert.  However I couldn't think of a case where I wouldn't want a
linefeed after an assert message, so it seems like Lua should do this out of
the box.

-John