default: check that 'install' script creates 'location'

slapos/recipe/build/__init__.py

@@ -282,6 +282,8 @@ class Script(EnvironMixin):
           else:
             self.logger.debug('Removing %r', path)
             rmtree(path)
+    if not os.path.exists(location):
+      raise zc.buildout.UserError('%r was not created' % location)
     return location
 
   def update(self):