Fix a bug in sinkProcessStdout handling stderr
Fix a bug in sinkProcessStdout handling stderr

Stderr was getting up in the stdout buffer which is provided to the
thrown ReadProcessException.

fizruk/stack,rrnewton/stack,vigoo/stack,meiersi-11ce/stack,MichielDerhaeg/stack,supermario/stack,mathhun/stack,narrative/stack,AndrewRademacher/stack,lukexi/stack,narrative/stack,AndreasPK/stack,rvion/stack,luigy/stack,Blaisorblade/stack,AndrewRademacher/stack,rrnewton/stack,robstewart57/stack,martin-kolinek/stack,harendra-kumar/stack,achernyak/stack,Heather/stack,deech/stack,luigy/stack,phadej/stack,AndreasPK/stack,juhp/stack,harendra-kumar/stack,deech/stack,rubik/stack,fizruk/stack,lukexi/stack,Blaisorblade/stack,vigoo/stack,keent/stack,meiersi-11ce/stack,martin-kolinek/stack,sjakobi/stack,MichielDerhaeg/stack,rvion/stack,rubik/stack,keent/stack,achernyak/stack,Fuuzetsu/stack,anton-dessiatov/stack,mrkkrp/stack,supermario/stack,anton-dessiatov/stack,sjakobi/stack,mathhun/stack,robstewart57/stack,Fuuzetsu/stack,juhp/stack,mrkkrp/stack,phadej/stack,Heather/stack