Auburn University canceled classes Wednesday following a threat. The menacing message was found scrawled on a men's restroom wall at the Haley Center.  A message posted on the university's website says authorities don't believe the threat is credible.  But the school says it is was suspending classes and other normal operations for a day because of anxiety among students and parents.  Wednesday marked the seventh anniversary of the deadly shooting rampage at Virginia Tech, although it's unclear if the threat was motivated by that event.   Normal operations at Auburn were expected to resume Thursday morning, university officials said.