iron-hmac is patterns_in_fns_without_body (new since stable, set to warn) + deny(warnings).
epoxy is inaccessible_extern_crate (was warn in stable, now deny).
tangle is invalid_type_param_default (was warn in stable, now deny).
nanomsg-sys is a spurious regression -- it appears nanomsg-sys changed between the two runs. I manually verified that all nanomsg-sys commits that compile on stable-2016-11-08 also compile on beta-2016-12-10.