[autoroll] Provide more detail when failing to decode a roller config
[autoroll] Provide more detail when failing to decode a roller config

Change-Id: I6df7e61e69e79a614eb40d6068ad119bb9530a3e
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/596587
Auto-Submit: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>
Commit-Queue: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>
Reviewed-by: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>
Commit-Queue: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot