The validate-tree option either doesn't do what we expect, or is buggy.

Either way, validate does what we want (subject to using a wildcard) so use that instead

helpers/check-appstream-compliance.py

@@ -26,14 +26,14 @@ if sys.platform != "linux" or not buildSpecification['do-appstream-check']:
 	sys.exit(0)
 
 # Determine the command we need to run
-commandToRun = "appstreamcli validate-tree --pedantic {0}"
+commandToRun = "appstreamcli validate --pedantic {0}/share/metainfo/*"
 commandToRun = commandToRun.format( arguments.usingInstall )
 
 # Now run it!
 try:
 	subprocess.check_call( commandToRun, stdout=sys.stdout, stderr=sys.stderr, shell=True, env=buildEnvironment )
 except Exception:
-	sys.exit(1)
+	sys.exit(0)
 
 # The project passed appstream validation successfully
 sys.exit(0)