Set result if sys.exit() is called by subcommand.

Allows the finally branch to make sure of the return code.

Change-Id: I7a796da5b60269cbd71aad953f1b9bb762b8eef8

main.py

@@ -198,6 +198,10 @@ class _Repo(object):
       else:
         print('error: project group must be enabled for the project in the current directory', file=sys.stderr)
       result = 1
+    except SystemExit as e:
+      if e.code:
+        result = e.code
+      raise
     finally:
       elapsed = time.time() - start
       hours, remainder = divmod(elapsed, 3600)