When you create a Lambda permission you send the __statement id__ as mandatory parameter.

https://docs.aws.amazon.com/lambda/latest/dg/API_AddPermission.html#API_AddPermission_RequestSyntax

However this id is generated by a random value. 

https://github.com/localstack/localstack/blob/b3917bf248b77ced8ef80a3d5c0561960066db5d/localstack/services/awslambda/lambda_api.py#L927

Due to this problem, the tools like Terraform or Ansible fail when it has to be retrieved to check the existence of this element.

If you agree I could make a PR with the fix and its test.
""" Get an existing event source mapping
        ---
        operationId: 'getEventSourceMapping'
        parameters:
            - name: 'request'
              in: body
    """
    mappings = event_source_mappings
    mappings = [m for m in mappings if mapping_uuid == m.get('UUID')]
    if len(mappings) == 0:
        return not_found_error()
    return jsonify(mappings[0])
@app.route('%s/event-source-mappings/' % PATH_ROOT, methods=['POST'])
def create_event_source_mapping():