Shorten traceback of protocol errors.

mila · pgjones · commit 2f7ba956615f · 2021-08-28T16:23:28.000Z
KeyError with "During handling of the above exception, another exception occurred:" is unnecessary in an exception chain.
diff --git a/h11/_state.py b/h11/_state.py
@@ -252,7 +252,7 @@ def _fire_event_triggered_transitions(self, role, event_type):
                 "can't handle event type {} when role={} and state={}".format(
                     event_type.__name__, role, self.states[role]
                 )
-            )
+            ) from None
         self.states[role] = new_state
 
     def _fire_state_triggered_transitions(self):

Original file line number	Diff line number	Diff line change
`@@ -252,7 +252,7 @@ def _fire_event_triggered_transitions(self, role, event_type):`
`252`	`252`	`"can't handle event type {} when role={} and state={}".format(`
`253`	`253`	`event_type.__name__, role, self.states[role]`
`254`	`254`	`)`
`255`		`- )`
	`255`	`+ ) from None`
`256`	`256`	`self.states[role] = new_state`
`257`	`257`
`258`	`258`	`def _fire_state_triggered_transitions(self):`