using injected response object

Scenario:
Invalid HTTP codes are coming in from a webservice (in our case 497). 
An exception is being thrown in HttpClient, if a constant with name STATUS_CODE_<codeId> is not existing in response entity. When setting a response object in the HTTP client containing the "missing" constant, i expected exactly this response object coming back from $client->send().

In The client the following happens:
```
$response = Response::fromString($response);
```

A new response object of type Zend\Http\Response is created on incoming response, instead of the injected one, which can be retrieved using $this->getResponse().

Current (dirty) Solution is to catch the exception and call the fromString method in the CustomResponse class containing the additional STATUS_CODE_<codeId>'s.