Adjust test for new argparse output

tests/test_cmdline.py

@@ -757,7 +757,7 @@ class TestCmdline(object):
         self.ok("destroy --help")
 
         self.fail("destroy")
-        self.contain("too few arguments")
+        self.contain("the following arguments are required")
 
         self.fail("destroy /no/such/stream")
         self.contain("no stream matched path")