Tomcat Uplaod AttributeError: can't set attribute

Hello,
when i use this : 

```
cli = MsfRpcClient(username="msf", password="test")
lista = cli.modules.exploits
exploit = cli.modules.use('exploit', 'multi/http/tomcat_mgr_upload')
```

i get : 
`AttributeError: can't set attribute
`

Why ?