Collapse and truncate the given text to fit in the given width.
The text first has its whitespace collapsed. If it then fits in
the *width*, it is returned as is. Otherwise, as many words
as possible are joined and then the placeholder is appended::
>>> textwrap.shorten("Hello world!", width=12)
'Hello world!'
>>> textwrap.shorten("Hello world!", width=11)
'Hello [...]'