Going back in MIDI time error: disappeared?

[Federico Bruni]

NR 1.2.6, Grace notes, section Known problems:

"""
Each grace note in MIDI output has a length of 1/4 of its actual 
duration. If the combined length of the grace notes is greater than the 
length of the preceding note a “Going back in MIDI time” error will be 
generated. Either make the grace notes shorter in duration, for example:

\acciaccatura { c'8[ d' e' f' g'] }
becomes:

\acciaccatura { c'16[ d' e' f' g'] }
"""

I'm trying to reproduce such an error, just to check if I've understood 
it correctly, but I can't.
The combined length of grace notes, in first example, is 5/8. So if I 
put a shorter note before the grace expression I should produce an error?

\version "2.17.10"

{
  c'16
  \acciaccatura { c'8[ d' e' f' g'] }
}

It's not working.
I think I'm totally missing the point.

Secondly, I can't find that message in the lilypond.pot file, even 
though I remember I've come across it some time ago:

cd po
git grep -i 'midi time'

Where is it?


Finally, searching the archives and the tracker I've found that I cannot 
reproduce in 2.17.10 the error in the examples posted. See for example:
http://code.google.com/p/lilypond/issues/detail?id=1412

Can you help me?
--
Federico