Credentials: use aggressive IAM timeout

[matthewkmayer]

If the credentials chain fails on finding environment or file based credentials, say from providing a bad credentials profile name, we're calling the IAM metadata service to find creds. If we're running on a dev laptop it will sit until it times out which is probably 60 seconds.

Let's drop that timeout to say 15 seconds.

[matthewkmayer]

This will be either set_write_timeout or set_read_timeout:

https://github.com/hyperium/hyper/blob/d32d35bbea947172224082e1f9b711022ce75e30/src/client/request.rs#L49

[matthewkmayer]

Looks like this feature in Rust, thus seen in Hyper, hasn't settled down quite yet: rust-lang/rust#27773 .

src/lib.rs:4:1: 4:22 error: #[feature] may not be used on the stable release channel
src/lib.rs:4 #![feature(duration)]

[matthewkmayer]

The rust-lang issue has been fixed and closed: I'm not sure if it's coming in Rust 1.4 or 1.5. Then Hyper will need to be updated to allow timeout to be specified and handled.

[matthewkmayer]

Our time crate is deprecated: https://github.com/rust-lang-deprecated/time . We should switch to the standard library: https://doc.rust-lang.org/std/time/struct.Duration.html .

This also means we'll need to bump our docs (README and/or CONTRIBUTING) to show we need Rust 1.5+.