Minor typo on PageMiddleware error message.
Minor typo on PageMiddleware error message.

jamesfoley/cms,lewiscollard/cms,jamesfoley/cms,danielsamuels/cms,dan-gamble/cms,danielsamuels/cms,dan-gamble/cms,etianen/cms,etianen/cms,lewiscollard/cms,jamesfoley/cms,lewiscollard/cms,danielsamuels/cms,jamesfoley/cms,etianen/cms,dan-gamble/cms