--- a/buttercup/checkout.py	Tue Nov 03 07:51:52 2020 -0800
+++ b/buttercup/checkout.py	Tue Nov 03 07:59:36 2020 -0800
@@ -25,25 +25,27 @@
                       help="install the packages")
     parser.add_option('--list', action="store_true", default=False,
                       help="list the source to be installed")
+    parser.add_option('--prefix',
+                      help="prefix or http://k0s.org/hg if not specified")
     options, args = parser.parse_args(args)
 
     # list sources if specified
     if options.list:
-        buttercup = Buttercup(srcdir=None)
+        buttercup = Buttercup(srcdir=None, prefix=options.prefix)
         sources = source.sources(buttercup.sources)
         for s in sources:
             print('%s: %s' % (s.directory_name(s.uri), s.uri))
-        sys.exit(0)
+        return
 
     # setup the src directory in a virtualenv
-    if 'VIRTUAL_ENV' in os.environ:
+    if 'VIRTUAL_ENV' not in os.environ:
         raise AssertionError("You must have a virtualenv activated")
     src = os.path.join(os.environ['VIRTUAL_ENV'], 'src')
     if not os.path.exists(src):
         os.mkdir(src)
 
     # grow a flower
-    buttercup = Buttercup(srcdir=src)
+    buttercup = Buttercup(srcdir=src, prefix=options.prefix)
 
     # clone/update the sources
     buttercup.install()
@@ -52,4 +54,4 @@
         buttercup.setup()
 
 if __name__ == '__main__':
-    main()
+    sys.exit(main() or 0)