Auto merge of #3991 - alexcrichton:better-errors, r=matklad
authorbors <bors@rust-lang.org>
Wed, 3 May 2017 19:38:36 +0000 (19:38 +0000)
committerbors <bors@rust-lang.org>
Wed, 3 May 2017 19:38:36 +0000 (19:38 +0000)
Improve configuration load errors

Add some more context information on the backtrace


Trivial merge