Fix exception introduced in 8b98e8f1425a.
Fix exception introduced in 8b98e8f1425a.

Some templates reference the url by their handler name, so renaming
an handler requires editing the HTML pages.

Original review was https://codereview.appspot.com/12820046/.

Review: https://codereview.appspot.com/12773046/

riannucci/rietveldv2,riannucci/rietveldv2