## CapabilityError


An operation was requested that the backend does not support.


Usage

``` python
CapabilityError(
    message,
    *,
    key=None,
    kind=None,
)
```


Raised, for example, when [open](testing.ObjectBackend.md#tether.testing.ObjectBackend.open) is asked for a writable handle on an object whose backend is not [FORK](testing.Capability.md#tether.testing.Capability.FORK)-capable.