DOC : PEP8 fixes in test_metrics
DOC : PEP8 fixes in test_metrics

FrancoisRheaultUS/dipy,StongeEtienne/dipy,villalonreina/dipy,FrancoisRheaultUS/dipy,matthieudumont/dipy,villalonreina/dipy,nilgoyyou/dipy,StongeEtienne/dipy,nilgoyyou/dipy,matthieudumont/dipy