use subprocess.Popen so xbsvgen does not require python 2.7
use subprocess.Popen so xbsvgen does not require python 2.7

chenm001/connectal,8l/connectal,csail-csg/connectal,csail-csg/connectal,8l/connectal,hanw/connectal,cambridgehackers/connectal,cambridgehackers/connectal,8l/connectal,hanw/connectal,hanw/connectal,cambridgehackers/connectal,cambridgehackers/connectal,hanw/connectal,chenm001/connectal,8l/connectal,csail-csg/connectal,8l/connectal,chenm001/connectal,chenm001/connectal,csail-csg/connectal,csail-csg/connectal,cambridgehackers/connectal,hanw/connectal,chenm001/connectal