raise exception if ipython parallel system is not installed
raise exception if ipython parallel system is not installed

git-svn-id: 24f545668198cdd163a527378499f2123e59bf9f@1628 ead46cd0-7350-4e37-8683-fc4c6f79bf00

dgellis90/nipype,arokem/nipype,dgellis90/nipype,carolFrohlich/nipype,fprados/nipype,arokem/nipype,gerddie/nipype,carlohamalainen/nipype,Leoniela/nipype,grlee77/nipype,carolFrohlich/nipype,JohnGriffiths/nipype,wanderine/nipype,mick-d/nipype,wanderine/nipype,satra/NiPypeold,sgiavasis/nipype,Leoniela/nipype,wanderine/nipype,glatard/nipype,mick-d/nipype_source,arokem/nipype,dmordom/nipype,iglpdc/nipype,rameshvs/nipype,dmordom/nipype,iglpdc/nipype,FCP-INDI/nipype,blakedewey/nipype,christianbrodbeck/nipype,FCP-INDI/nipype,mick-d/nipype,blakedewey/nipype,mick-d/nipype_source,mick-d/nipype_source,dmordom/nipype,carolFrohlich/nipype,blakedewey/nipype,sgiavasis/nipype,grlee77/nipype,carlohamalainen/nipype,glatard/nipype,glatard/nipype,JohnGriffiths/nipype,wanderine/nipype,sgiavasis/nipype,mick-d/nipype,pearsonlab/nipype,rameshvs/nipype,arokem/nipype,FredLoney/nipype,iglpdc/nipype,FredLoney/nipype,gerddie/nipype,grlee77/nipype,pearsonlab/nipype,satra/NiPypeold,grlee77/nipype,carolFrohlich/nipype,iglpdc/nipype,gerddie/nipype,gerddie/nipype,rameshvs/nipype,sgiavasis/nipype,Leoniela/nipype,JohnGriffiths/nipype,fprados/nipype,dgellis90/nipype,dgellis90/nipype,pearsonlab/nipype,glatard/nipype,rameshvs/nipype,mick-d/nipype,FredLoney/nipype,christianbrodbeck/nipype,blakedewey/nipype,carlohamalainen/nipype,FCP-INDI/nipype,FCP-INDI/nipype,JohnGriffiths/nipype,pearsonlab/nipype,fprados/nipype