regression: --demo

[Alexandre Detiste]

I reply to myself.

Do you like the "\" ? Some hates it and prefer wrapping the thing in parenthesis.

> the --demo flag doens't work anymore
> 
> tchet at antec:~/game-data-packager$ ./game-data-packager wolf3d --demo          
> generated "/home/tchet/game-data-packager/wolf3d-full-data_39_all.deb"

--- a/lib/game_data_packager/__init__.py
+++ b/lib/game_data_packager/__init__.py
@@ -1977,7 +1977,8 @@ class GameData(object):
         ready = set()
 
         for package in possible:
-            if package.demo_for and self.packages[package.demo_for] in possible:
+            if package.demo_for and self.packages[package.demo_for] in possible \
+               and not build_demos:
                 # no point in packaging the demo if we have the full
                 # version