### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

When attempting to sign some document using Localstack KMS inside a lambda container (also running on localstack), the localstack KMS listener returns some unknown error.

The KMS key and lambda containers have been created from the same CDK app deploy, and I can see all the resources in the localstack web console.

The test application I'm using to prove this behaviour is available here:
https://github.com/LukaHedt/localstack_kms_test

Instructions to run are in the main Readme, and the `/localstack/Readme.md` file.

`aws-sdk` returns an unknown error, and the localstack docker logs that I receive are available here:
https://pastebin.com/58Z3fXi3

Have done an amount of testing and can confidently claim the following:
- Have tested on multiple machines with the same outcome
- Doesn’t make a difference if I specify an ARN or a KeyID in the signing request
- Downgrading localstack versions either didn’t make a difference, or I couldn’t actually deploy a localstack container with version 0.12.20 or lower.

### Expected Behavior

KMS Sign should return a signature for the given payload.

### How are you starting LocalStack?

With a docker-compose file

### Steps To Reproduce

Test application demonstrating the current behaviour is available here:

https://github.com/LukaHedt/localstack_kms_test

Full instructions to run are in the `/localstack/Readme.md` file.


### Environment

```markdown
- OS: MacOS Monteray 12.3
- LocalStack: 0.14.0
```


### Anything else?

_No response_
self, error: ServiceException, operation_model: OperationModel
    ) -> HttpResponse:
        """
        Takes an error instance and serializes it to an actual HttpResponse.
        Therefore this method is used for errors which should be serialized and transmitted to the calling client.
        :param error: to serialize
        :param operation_model: specification of the service & operation containing information about the shape of the
                                service's output / response
        :return: HttpResponse which can be sent to the calling client
        :raises: ResponseSerializerError (either a ProtocolSerializerError or an UnknownSerializerError)
        """
        serialized_response = self._create_default_response(operation_model)
        if isinstance(error, CommonServiceException):
            # Not all possible exceptions are contained in the service's specification.
            # Therefore, service implementations can also throw a "CommonServiceException" to raise arbitrary /
            # non-specified exceptions (where the developer needs to define the data which would usually be taken from
            # the specification, like the "Code").
            code = error.code
            sender_fault = error.sender_fault
            status_code = error.status_code
            shape = None
        else:
            # It's not a CommonServiceException, the exception is being serialized based on the specification
            # The shape name is equal to the class name (since the classes are generated from the shape's name)
            error_shape_name = error.__class__.__name__
            # Lookup the corresponding error shape in the operation model