Explicit return value from main

Rather than sometimes returning an integer, sometimes a boolean and
sometimes implicitly returning None, always return 0 for success and 1
for failure.

No behavior change for the program as a whole, since the None/True/False
values were implicitly converted to the desired numerical value.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>

scripts/config.py

@@ -452,7 +452,7 @@ if __name__ == '__main__':
                 value = config[args.symbol]
                 if value:
                     sys.stdout.write(value + '\n')
-            return args.symbol not in config
+            return 0 if args.symbol in config else 1
         elif args.command == 'set':
             if not args.force and args.symbol not in config.settings:
                 sys.stderr.write("A #define for the symbol {} "
@@ -465,6 +465,7 @@ if __name__ == '__main__':
         else:
             config.adapt(args.adapter)
         config.write(args.write)
+        return 0
 
     # Import modules only used by main only if main is defined and called.
     # pylint: disable=wrong-import-position