Fix unhashable exception types

Author: asottile

src/werkzeug/debug/tbtools.py

@@ -248,11 +248,11 @@ def __init__(self, exc_type, exc_value, tb):
         memo = set()
         while True:
             self.groups.append(Group(exc_type, exc_value, tb))
-            memo.add(exc_value)
+            memo.add(id(exc_value))
             if PY2:
                 break
             exc_value = exc_value.__cause__ or exc_value.__context__
-            if exc_value is None or exc_value in memo:
+            if exc_value is None or id(exc_value) in memo:
                 break
             exc_type = type(exc_value)
             tb = exc_value.__traceback__

tests/test_debug.py

@@ -371,3 +371,14 @@ def test_chained_exception_cycle():
     # if cycles aren't broken, this will time out
     tb = Traceback(TypeError, error, error.__traceback__)
     assert len(tb.groups) == 2
+
+
+def test_non_hashable_exception():
+    class MutableException(ValueError):
+        __hash__ = None
+
+    try:
+        raise MutableException()
+    except MutableException:
+        # previously crashed: `TypeError: unhashable type 'MutableException'`
+        Traceback(*sys.exc_info())