Recognizing a given path whose route uses request.env within constraint  

Now you can call `Rails.application.routes.recognize_path` passing `request.env` as the second parameter. 

It prevents a possible `NoMethodError for nil` when you are using `request.env[‘some_custom_key’].some_method` within route constraint. For example:

```
match "/some_path", to: "some_controller#some_action", 
            constraint: ->(req) { req['warden'].user }
```
I was talking with @tenderlove and he said he is working to remove this method. What he explained to me we don't use this method during the route recognition and it's that this method and the method that actually examines the requests path come up with different return values.