Working on Rails upgrade to versions 4.2 recently, I came across the following error message:
NoMethodError undefined method '' for "image":Sass::Script::Value::String
Backtrace pointed at nonrelevant line, so I had no idea where to start searching. Fortunately I found the solution at https://github.com/rails/sprockets-rails/issues/279.
It seems like the issue was my
asset-url method using old two-argument call:
I removed the last argument according to http://guides.rubyonrails.org/upgrading_ruby_on_rails.html depreciation notice and it worked like charm.