[scribus] Multiple sessions.

[Roger]

 >> That's a lot of platform specific messing around, though, for a pretty
 >> >> trivial feature. Personally I wouldn't bother.
 >> >>
 > >
 > > A simple way would be to create a lock file the sole purpose of which
 > > is to indicate that Scribus has already opened the file.

Lock files are IMO about the *worst* way of doing it.

Why not a simple Pop Up that says "This file is already open -- Opening another 
instance may introduce editing errors - Continue Y/N"
then leave it up to the user.
Roger