Merge commit 'lamby/master' into merge

* commit 'lamby/master':
  Add missing "utils" import (used in security conditional)
  No need to assign to a local now that @session_wrapper does the cleanup
  Avoid calling .count(); call .one() and catch the exception.
  Fix Archive.__repr__
  Factor out most common session handling into decorator.

Signed-off-by: Joerg Jaspert <joerg@debian.org>