Silence the "ended normally" messages from MOPAC
Silence the "ended normally" messages from MOPAC

These are printed directly to the standard error stream,
and are not errors or even warnings. This captures them
and suppresses them. If something unexpected appears in 
stderr then it is reported to the RMG log.
pierrelb/RMG-Py,nickvandewiele/RMG-Py,pierrelb/RMG-Py,nyee/RMG-Py,nyee/RMG-Py,nickvandewiele/RMG-Py