How to get GraphQL error objects using GraphQLView in 2.0.0?

Hello,

We are using this library to add graphql support to our flask app. We used to have version 1.3.1 installed and the following view code was working correctly:

```
class AppGraphQLView(GraphQLView):
def execute_graphql_request(self, *args, **kwargs):
"""Extract any exceptions and send them to Raygun"""
result = super().execute_graphql_request(*args, **kwargs)

if result is not None and result.errors:
send_errors_to_raygun(result.errors)

return result
```

We've recently updated to version 2.0.0 of this library, and this caused our errors to not be sent to raygun, because our function is no longer called.. I discovered that the whole of GraphQLView has been refactored to not include `execute_graphql_request` anymore so I tried using `dispatch_request` instead.

However, `dispatch_request` returns a json object and any errors have only the message, no stacktrace or any other important information we would need to send to raygun.

I have tried to replicate this functionality without overwriting GraphQLView's implementation of `execute_graphql_request`, by using middleware instead:
```
def error_reporting_middleware(next, root, info, **kwargs):

result = next(root, info, **kwargs)

if result.is_rejected:
send_errors_to_raygun([result.reason])

return result
```
This kinda works, but I was wondering if there is a similar way to do it using the refactored GraphQLView in v2.0.0.

Thanks!