Default to patternxml when patternxml or groupxml isn't defined.

Signed-off-by: Marko Saukko <marko.saukko@jollamobile.com>

repomd-pattern-builder.py

@@ -160,8 +160,8 @@ def merge_patterns(patterns_dir, version, release, outputdir, newobsapi):
 	(options, args) = parser.parse_args()
 
 	if (not options.groupxml and not options.patternxml):
-		print "Error: you need to use either --patternxml or --groupxml."
-		exit(1)
+		# Default to patternxml.
+		options.patternxml = True
 
 	if (not options.patterndir or not os.path.exists(options.patterndir)):
 		print "Error: Pattern dir '%s' doesn't exist." % (options.patterndir)