Python 2, 24 bytes
lambda s:s in(s*2)[1:-1]
Shamelessly stolen from xnor's answer to the original question.
More intuitive version:
Python 2, 59 55 53 bytes
lambda s:s in[len(s)/i*s[:i]for i in range(1,len(s))]
Boring regex version:
Python 2, 44 bytes
lambda s:re.match(r'(.+)\1+$',s)>0
import re