Fix #279, let the user know when there is a problem.
Fix #279, let the user know when there is a problem.

jekyll/jekyll-assets,mattbeedle/jekyll-assets,mattbeedle/jekyll-assets,jeremy/jekyll-assets,jekyll-assets/jekyll-assets,jeremy/jekyll-assets,mattbeedle/jekyll-assets,jekyll/jekyll-assets,jeremy/jekyll-assets,jekyll-assets/jekyll-assets,mattbeedle/jekyll-assets,jekyll/jekyll-assets,jeremy/jekyll-assets,jekyll/jekyll-assets,jekyll-assets/jekyll-assets