Fix broken maintenance mode
Maintenance mode has been broken since r7fe19ebfe0d3 (Thu Jun 4)
"Display caught errors on the page itself", fix it by passing the
site entity, rather than the site module to isActivePeriod.
# use glob syntax.
syntax: glob
*.pyc
*.zip
*~
.project
.pydevproject
app.yaml
build
tests/coverageResults
*,cover
tests/.coverage
*.git
*.egg-info
eggs
parts
.installed.cfg
bin
develop-eggs
.gitignore
.DS_Store
.settings