-page = urlopener.open('https://launchpad.net/ubuntu/+source/' + package).read()
-m = re.search('"/ubuntu/%s/\+source/%s/(\d[^"]+)"' % (release, package), page)
+try:
+ page = urlopener.open('https://launchpad.net/ubuntu/+source/' + package).read()
+except urllib2.HTTPError:
+ print >> sys.stderr, 'This source does not appear to exist in Ubuntu'
+ sys.exit(1)
+
+m = re.search('"/ubuntu/%s/\+source/%s/(\d[^"]+)"' % (release, package.replace('+', '\+')), page)