Adds Reponse.has_body.

[martinth]

This is a result of the discussion in [https://github.com/Pylons/pyramid/issues/2625](Pyramid issue 2625).

Purpose of this property is to allow users to check if the Response has a body without forcing an evaulation of the underlying app_iter. This is handy if you wan't to create a streaming response where the app_iter itself is lazy (i.e. streams data over a socket) or the app_iter can only read once.

It's pretty much the same code as @bertjwregeer suggested but I added it as property rather than es method because I figured that it's fits better in the overall class design this way. The relevant changes for Pyramid will be done later.

[digitalresistor]

👍

[mmerickel]

This looks great. Just to bikeshed for a quick second... response.has_body could be construed to mean something like whether the status code says it should have a body or not. So I'm just curious if there's a more accurate name for this property that we could come up with. So far all I've got is... is_body_empty?

[martinth]

You have a point. It could indeed cause confusion if you only look at the property name (which is something I totally have done in the past). is_body_empty is probably the most obvious choice for an alternative but I don't think it's a bad one.

[digitalresistor]

I'd be okay with the rename. I could see the confusion happening...

[mmerickel]

is_body_set ?

[mmerickel]

I think I'm also fine with has_body. I think it's pretty easy to explain its behavior if there is any confusion.

[digitalresistor]

There is currently no checking if the user attempts to send a Response with an HTTP code that does not allow for a body. This is something that I may want to change in the future...

I am okay with either one. is_body_set or has_body both work for me. I'll let it simmer for a little bit longer and then go ahead and merge it.