Specify sass ~> 3.5 in Gemfile

Gemfile

@@ -277,6 +277,7 @@ gem 'webpack-rails', '~> 0.9.10'
 gem 'rack-proxy', '~> 0.6.0'
 
 gem 'sass-rails', '~> 5.0.6'
+gem 'sass', '~> 3.5'
 gem 'uglifier', '~> 2.7.2'
 
 gem 'addressable', '~> 2.5.2'

Gemfile.lock

@@ -1129,6 +1129,7 @@ DEPENDENCIES
   rufus-scheduler (~> 3.4)
   rugged (~> 0.27)
   sanitize (~> 4.6)
+  sass (~> 3.5)
   sass-rails (~> 5.0.6)
   scss_lint (~> 0.56.0)
   seed-fu (~> 2.3.7)

Gemfile.rails4.lock

@@ -1119,6 +1119,7 @@ DEPENDENCIES
   rufus-scheduler (~> 3.4)
   rugged (~> 0.27)
   sanitize (~> 4.6)
+  sass (~> 3.5)
   sass-rails (~> 5.0.6)
   scss_lint (~> 0.56.0)
   seed-fu (~> 2.3.7)