As long as we support 2.7 we have to use tostring().

rohe · rohe · commit f719a002779a · 2019-06-11T11:34:57.000+02:00
diff --git a/tests/test_4_jwe.py b/tests/test_4_jwe.py
@@ -25,7 +25,7 @@
 
 
 def intarr2bytes(arr):
-    return array.array('B', arr).tobytes()
+    return array.array('B', arr).tostring()
 
 
 def bytes2intarr(bts):
