Finally, I have upgraded to the latest version 0.9.0-2 but I have still the same problem. When I execute pySafe it opens the window and then it closes whitout asking for password.
I also execute /opt/pysafe/pysafe in a terminal and nothing happens : no window appears, no error message it just returned to the prompt.

Any idea ?

PS: I tried to install an old version but the links doesn't work anymore.