Replace assertRaisesRegex by assertRaises
Replace assertRaisesRegex by assertRaises

The unittest.assertRaisesRegexp function of Python2.7 has been
renamed to assertRaisesRegex in current versions of Python3.
To avoid this compatibility issue and in line with
[this issue](https://github.com/exercism/xpython/issues/30)
I replace these assertions with the assertRaises function.

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