Weird issue when using "with SessionToken"

[konoufo]

Hello guys !
This line raises a KeyError:
del ACCESS_KEYS['session_token']
It's in parse_rest/connection.py in exit method of class SessionToken.
It's executed when leaving this [familiar] with block in my code:
with SessionToken(token): user = User.current_user()

It doesn't make much sense given what's happening in enter. If anybody has an idea, it would be very much appreciated.