Change confirmation message to reflect current CMS

In my tests, publishing an unpublished page that is not active in the menu is *not* set active in the menu when you published (thankfully!), so this confirmation message appears out of date.
Move context assignment to only where it is required
Merge pull request #3139 from mkoistinen/move_context_assignment

Move context assignment to only where it is required
Cast site_id to int
Sorry, no more long in Python 3
Hi pyflakes, stop nagging, please!
Revert to isinstance check
Merge pull request #3129 from mkoistinen/publish_confirmation_msg

Change confirmation message to reflect current CMS
Merge pull request #3140 from yakky/feature/site_id

Cast site_id to int