[Sqlalchemy-tickets] Issue #2973: Event removal not working (zzzeek/sqlalchemy)

[Konsta V. <iss...@bi...>]

New issue 2973: Event removal not working
https://bitbucket.org/zzzeek/sqlalchemy/issue/2973/event-removal-not-working

Konsta Vesterinen:

Very simple test scenario:


```
#!python


import sqlalchemy as sa


@sa.event.listens_for(sa.orm.mapper, 'instrument_class')
def my_listener(mapper, cls):
    pass


sa.event.remove(
    sa.orm.mapper, 'instrument_class', my_listener
)
```

This throws a ValueError:

```
#!python

    def remove(self, event_key):
        target = event_key.dispatch_target
        stack = [target]
        while stack:
            cls = stack.pop(0)
            stack.extend(cls.__subclasses__())
            if cls in self._clslevel:
>               self._clslevel[cls].remove(event_key.fn)
E               ValueError: list.remove(x): x not in list

```

Maybe the `event_key.fn` should be `event_key.fn_wrap` instead?