Fix method of dropping the reference to the exception

Author: pR0Ps

Lib/contextlib.py

@@ -155,6 +155,8 @@ def __enter__(self):
             raise RuntimeError("generator didn't yield") from None
 
     def __exit__(self, typ, value, traceback):
+        # don't keep the stored exception alive unnecessarily
+        self.exc_context, exc_context = None, self.exc_context
         if typ is None:
             try:
                 next(self.gen)
@@ -164,7 +166,6 @@ def __exit__(self, typ, value, traceback):
                 try:
                     raise RuntimeError("generator didn't stop")
                 finally:
-                    del self.exc_context
                     self.gen.close()
         else:
             if value is None:
@@ -177,7 +178,7 @@ def __exit__(self, typ, value, traceback):
                 # context here. In order to make the context manager behave
                 # like a normal function we set the current exception context
                 # to what it was during the context manager's __enter__
-                _set_current_exception(self.exc_context)
+                _set_current_exception(exc_context)
                 self.gen.throw(value)
             except StopIteration as exc:
                 # Suppress StopIteration *unless* it's the same exception that
@@ -216,7 +217,6 @@ def __exit__(self, typ, value, traceback):
             try:
                 raise RuntimeError("generator didn't stop after throw()")
             finally:
-                del self.exc_context
                 self.gen.close()
 
 class _AsyncGeneratorContextManager(