The problem is actually on Tkinter side, not really tcl/tk fault here.
Tkinter should be formatting that text option as "{text here}" when the
value contains one or more spaces (it is actually fine to use this tcl
formatting when there are no spaces either).

To try this yourself, just change text to:
text = "{sample text with spaces}"

I can't look at Tkinter source right now to propose a correct solution,
but will do later (today hopefully).