test.py: return proper exit code to shell on failure
test.py: return proper exit code to shell on failure

This change helps downstream packagers make the package build fail
if a test fails.

fgregg/scrapelib,h4ck3rm1k3/scrapelib,pombredanne/scrapelib,dvogel/scrapelib,arowla/scrapelib,olberger/scrapelib,h4ck3rm1k3/scrapelib,JoeGermuska/scrapelib,jamesturk/scrapelib,sunlightlabs/scrapelib,olberger/scrapelib,arowla/scrapelib,fgregg/scrapelib,JoeGermuska/scrapelib,dvogel/scrapelib