It appears that Heroku recently changed the syntax for the BUNDLE_WITHOUT config variable.
The cached version of this [page] (http://docs.heroku.com/bundler) still shows the old syntax where the environment names are separated by spaces:
heroku config:add BUNDLE_WITHOUT="development test"
The current version shows them separated with a colon:
heroku config:add BUNDLE_WITHOUT="development:test"
I remembered this error when I initially deployed my app to Heroku. linecache19 was being installed as a dependency of ruby-debug19 which was declared in the bundler development group. I added the BUNDLE_WITHOUT config variable to Heroku and it solved the problem.
The problem came back this morning and I noticed the change above in the Heroku docs.blog comments powered by Disqus