Refactoring error handling.
Refactoring error handling.

gitenberg-dev/HTMLBook,macmillanpublishers/HTMLBook,gitenberg-dev/HTMLBook,mushroomgithub/HTMLBook,wastemobile/HTMLBook,macmillanpublishers/HTMLBook,wastemobile/HTMLBook,oreillymedia/HTMLBook,macmillanpublishers/HTMLBook,gitenberg-dev/HTMLBook,oreillymedia/HTMLBook,mushroomgithub/HTMLBook,mushroomgithub/HTMLBook,oreillymedia/HTMLBook