Remove failure dependency, or at least disable the `backtrace` default feature
This crate uses
failure, which itself uses by default the
backtrace crate. That can cause problems when building in some architectures and OSes.
It'd be great to use
default-features = false for that dependency if it's not required.
See https://bugzilla.mozilla.org/show_bug.cgi?id=1591564#c30 for practical problems this causes. redox_users is the only crate that doesn't use default-features = false on Mozilla.