RF: use sequences for run_command script tester
RF: use sequences for run_command script tester

`run_command` was using strings rather than sequences passing in the
``Popen`` constructor.  This blows up when there are space in the passed
paths.  Use the sequence command definition instead.

Messaoud-Boudjada/dipy,nilgoyyou/dipy,villalonreina/dipy,samuelstjean/dipy,samuelstjean/dipy,matthieudumont/dipy,FrancoisRheaultUS/dipy,beni55/dipy,sinkpoint/dipy,rfdougherty/dipy,nilgoyyou/dipy,mdesco/dipy,JohnGriffiths/dipy,jyeatman/dipy,beni55/dipy,StongeEtienne/dipy,demianw/dipy,demianw/dipy,mdesco/dipy,jyeatman/dipy,villalonreina/dipy,matthieudumont/dipy,Messaoud-Boudjada/dipy,sinkpoint/dipy,JohnGriffiths/dipy,oesteban/dipy,samuelstjean/dipy,oesteban/dipy,FrancoisRheaultUS/dipy,rfdougherty/dipy,StongeEtienne/dipy