Fix test_parzenhist 
Fix test_parzenhist 

Fix test_parzenhist to take care of a few PEP8 errors.
FrancoisRheaultUS/dipy,matthieudumont/dipy,villalonreina/dipy,nilgoyyou/dipy,FrancoisRheaultUS/dipy,villalonreina/dipy,StongeEtienne/dipy,matthieudumont/dipy,nilgoyyou/dipy,StongeEtienne/dipy