--- a/testing/mozharness/external_tools/purgelong.py
+++ b/testing/mozharness/external_tools/purgelong.py
@@ -48,17 +48,17 @@ else:
 
 
 def unlink_wrapper(unlink_orig, fn, ui):
     '''Calls the original unlink function, and if that fails, calls
     unlink_long'''
     try:
         ui.debug('calling unlink_orig %s\n' % fn)
         return unlink_orig(fn)
-    except WindowsError, e:
+    except WindowsError as e:
         # windows error 3 corresponds to ERROR_PATH_NOT_FOUND
         # only handle this case; re-raise the exception for other kinds of
         # failures
         if e.winerror != 3:
             raise
         ui.debug('caught WindowsError ERROR_PATH_NOT_FOUND; '
                  'calling unlink_long %s\n' % fn)
         return unlink_long(fn)