Fix erroneous unused variable warning

build

@@ -643,7 +643,7 @@ if 'clean' in targets:
       disp ('delete app: ' + appname + '\n')
       try:
         shutil.rmtree (appname)
-      except OSError as excp:
+      except OSError as excp: # pylint: disable=unused-variable
         disp ('error deleting app "' + appname + '": ' + os.strerror (excp.errno))
 
   sys.exit (0)