Moved detailed exception message to more efficient place.
Moved detailed exception message to more efficient place.

The detailed exception message introduced a couple of commits ago was 
generated for every species that does not have gauche, 1-5, or 'other' 
corrections. A significant fraction of CPU time was spent formatting this
message which is never seen. I have moved it so only when it is an actual
error that would be uncaught is the detail generated and printed.
faribas/RMG-Py,enochd/RMG-Py,KEHANG/RMG-Py,pierrelb/RMG-Py,faribas/RMG-Py,chatelak/RMG-Py,nickvandewiele/RMG-Py,enochd/RMG-Py,pierrelb/RMG-Py,nyee/RMG-Py,comocheng/RMG-Py,nyee/RMG-Py,KEHANG/RMG-Py,chatelak/RMG-Py,nickvandewiele/RMG-Py,comocheng/RMG-Py