fix(rustup): workaround rustlang bug
fix(rustup): workaround rustlang bug

Due to https://github.com/rust-lang/rust/issues/22252, r-value
temporaries outlive the lifetimes of variables bound with let
statements in a function body. Because of this, device.rs fails to
compile against newer rustc nightlies.

This implements a simple workaround that binds the result of the match
in `request_code` to a local variable before returning it. This allows
it to have the same lifetime as `req` in one of the previous let
bindings.

Narfinger/yup-oauth2,dermesser/yup-oauth2,dermesser/yup-oauth2