Update leap test
Update leap test

The use of self.assertFalse() passes True when a None value is given to the Test case. To solve this issue the use of self.assertIs() gives
more certitude that the Test case will pass with the right answer.

wobh/xpython,pombredanne/xpython,smalley/python,exercism/xpython,oalbe/xpython,pombredanne/xpython,outkaj/xpython,smalley/python,N-Parsons/exercism-python,de2Zotjes/xpython,pheanex/xpython,behrtam/xpython,outkaj/xpython,N-Parsons/exercism-python,ZacharyRSmith/xpython,orozcoadrian/xpython,mweb/python,Peque/xpython,oalbe/xpython,rootulp/xpython,jmluy/xpython,mweb/python,exercism/python,exercism/python,wobh/xpython,ZacharyRSmith/xpython,exercism/xpython,rootulp/xpython,jmluy/xpython,de2Zotjes/xpython,Peque/xpython,orozcoadrian/xpython,behrtam/xpython,pheanex/xpython