Fix python3 exception when ctrl-c tools/trace.py
Fix python3 exception when ctrl-c tools/trace.py

The way to do exception printing in python2/3 compatible way is using
sys.exc_info()[0/1].

romain-intel/bcc,mkacik/bcc,tuxology/bcc,tuxology/bcc,iovisor/bcc,mcaleavya/bcc,mkacik/bcc,brendangregg/bcc,mkacik/bcc,tuxology/bcc,tuxology/bcc,iovisor/bcc,tuxology/bcc,zaafar/bcc,brendangregg/bcc,brendangregg/bcc,brendangregg/bcc,romain-intel/bcc,brendangregg/bcc,iovisor/bcc,shodoco/bcc,mcaleavya/bcc,iovisor/bcc,mkacik/bcc,shodoco/bcc,zaafar/bcc,mkacik/bcc,romain-intel/bcc,zaafar/bcc,zaafar/bcc,shodoco/bcc,mcaleavya/bcc,shodoco/bcc,zaafar/bcc,mcaleavya/bcc,mcaleavya/bcc,iovisor/bcc,romain-intel/bcc,romain-intel/bcc,shodoco/bcc