Probably related to #1643 , but what appears to happen seems different (at least the error is).

From what I can see, the lambda executes successfully, but then fails to return the result, returning the following instead:
```json
{
    "Type": "Server",
    "message": "Error executing Lambda function arn:aws:lambda:ap-northeast-1:000000000000:function:service-stage-functionName: module 'botocore.errorfactory' has no attribute 'ResourceAlreadyExistsException' Traceback (most recent call last):\n  File \"/opt/code/localstack/localstack/services/awslambda/lambda_executors.py\", line 106, in _store_logs\n    logs_client.create_log_group(logGroupName=log_group_name)\n  File \"/opt/code/localstack/.venv/lib/python3.6/site-packages/botocore/client.py\", line 357, in _api_call\n    return self._make_api_call(operation_name, kwargs)\n  File \"/opt/code/localstack/.venv/lib/python3.6/site-packages/botocore/client.py\", line 661, in _make_api_call\n    raise error_class(parsed_response, operation_name)\nbotocore.errorfactory.ResourceAlreadyExistsException: An error occurred (ResourceAlreadyExistsException) when calling the CreateLogGroup operation: The specified log group already exists\n\nDuring handling of the above exception, another exception occurred:\n\nTraceback (most recent call last):\n  File \"/opt/code/localstack/localstack/services/awslambda/lambda_api.py\", line 339, in run_lambda\n    event, context=context, version=version, asynchronous=asynchronous)\n  File \"/opt/code/localstack/localstack/services/awslambda/lambda_executors.py\", line 81, in execute\n    return do_execute()\n  File \"/opt/code/localstack/localstack/services/awslambda/lambda_executors.py\", line 70, in do_execute\n    self._store_logs(func_details, log_output, invocation_time)\n  File \"/opt/code/localstack/localstack/services/awslambda/lambda_executors.py\", line 107, in _store_logs\n    except botocore.errorfactory.ResourceAlreadyExistsException:\nAttributeError: module 'botocore.errorfactory' has no attribute 'ResourceAlreadyExistsException'\n",
    "__type": "InternalFailure"
}
```

Looking at the localstack end I see the following log:

```
...(lambda execution log, SUCCESS etc)...
> REPORT RequestId: 00e1e000-0e00-000c-0000-8ccf00ab00ba	Duration: 52.74 ms	Billed Duration: 100 ms	Memory Size: 1536 MB	Max Memory Used: 5 MB	
> nohup: failed to run command 'python': No such file or directory
2019-10-25T11:46:25:WARNING:localstack.services.awslambda.lambda_api: Error executing Lambda function arn:aws:lambda:ap-northeast-1:000000000000:function:service-stage-functionName: module 'botocore.errorfactory' has no attribute 'ResourceAlreadyExistsException' Traceback (most recent call last):
  File "/opt/code/localstack/localstack/services/awslambda/lambda_executors.py", line 106, in _store_logs
    logs_client.create_log_group(logGroupName=log_group_name)
  File "/opt/code/localstack/.venv/lib/python3.6/site-packages/botocore/client.py", line 357, in _api_call
    return self._make_api_call(operation_name, kwargs)
  File "/opt/code/localstack/.venv/lib/python3.6/site-packages/botocore/client.py", line 661, in _make_api_call
    raise error_class(parsed_response, operation_name)
botocore.errorfactory.ResourceAlreadyExistsException: An error occurred (ResourceAlreadyExistsException) when calling the CreateLogGroup operation: The specified log group already exists

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/opt/code/localstack/localstack/services/awslambda/lambda_api.py", line 339, in run_lambda
    event, context=context, version=version, asynchronous=asynchronous)
  File "/opt/code/localstack/localstack/services/awslambda/lambda_executors.py", line 81, in execute
    return do_execute()
  File "/opt/code/localstack/localstack/services/awslambda/lambda_executors.py", line 70, in do_execute
    self._store_logs(func_details, log_output, invocation_time)
  File "/opt/code/localstack/localstack/services/awslambda/lambda_executors.py", line 107, in _store_logs
    except botocore.errorfactory.ResourceAlreadyExistsException:
AttributeError: module 'botocore.errorfactory' has no attribute 'ResourceAlreadyExistsException'
```

Will update if I am able to create an easily reproducible case!
self._send_cors_headers()
                    self.end_headers()
                    return
            
            if response is None:
                forward_headers['Connection'] = forward_headers.get('Connection') or 'close'
                data_to_send = self.data_bytes
                request_url = proxy_url
                if modified_request:
                    if modified_request.url:
                        request_url = '%s%s' % (forward_url, modified_request.url)
                    data_to_send = modified_request.data
                response = self.method(request_url, data=data_to_send,
                    headers=forward_headers, stream=True)
                
                if not response._content_consumed and response.raw:
                    response._content = response.raw.read()
            
            if self.proxy.update_listener:
                kwargs = {
                    'method': method,
                    'path': path,
                    'data': data,
                    'headers': forward_headers,
                    'response': response
                }
                if 'request_handler' in inspect.getargspec(self.proxy.update_listener.return_response)[0]:
                    
                    
                    kwargs['request_handler'] = self