Implement 'Send' for diesel::result::Error

[freiguy1]

I'm working on a web app using iron and there's a macro itry! which wraps std::error::Errors in iron's IronError (documentation). When attempting to use itry! on a bit of code which returns an error containing a diesel::result::Error I get a nasty warning about implementing Send for an this error:

<iron macros>:7:1: 7:26 error: the trait `core::marker::Send` is not implemented for the type `std::error::Error + 'static` [E0277]
<iron macros>:7 $ crate:: IronError:: new ( err , $ modifier ) ) } )
                ^~~~~~~~~~~~~~~~~~~~~~~~~
<iron macros>:2:1: 2:61 note: in this expansion of itry! (defined in <iron macros>)
src/league/get_by_id.rs:23:5: 23:23 note: in this expansion of itry! (defined in <iron macros>)
<iron macros>:7:1: 7:26 help: run `rustc --explain E0277` to see a detailed explanation
<iron macros>:7:1: 7:26 note: `std::error::Error + 'static` cannot be sent between threads safely
<iron macros>:7:1: 7:26 note: required because it appears within the type `Box<std::error::Error + 'static>`
<iron macros>:7:1: 7:26 note: required because it appears within the type `diesel::result::Error`
<iron macros>:7:1: 7:26 note: required by `iron::error::IronError::new`
error: aborting due to previous error

this happens when trying to use itry!(do_thing()) where do_thing is:

fn do_thing() -> Result<u32, ::diesel::result::Error> {
    Ok(13);
}

Other errors do not show the same behavior even though they don't explicitly implement Send. Perhaps there is something in diesel's Error which isn't thread safe?