Fix can not start rails server when upgrade sprockets to 2.12.3

Fix_sprockets_rails_s

Hi,

I got it sorted. Here is what I did to fix it:

I found a revision in the Sprockets Github repo
(https://github.com/sstephenson/sprockets/commit/743c1b1a6433195e440e2d863e5d4767cc41271a)
when searching for a fix for the undefined method error relating to
default_mime_type. I then applied this change to the following ruby
scripts
in the sprockets 2.11.0 gem directory: jst_processor, sass_compressor,
closure_compressor, uglifier_compressor, sass_template, scss_template.

I then edited my GemFile to activate therubyracer within my gem
environment.

Thanks for your assistance.

Peter

from: https://www.ruby-forum.com/topic/4460060