Recently I came accross with one nasty error on Heroku when recreating some old web app that i were developing
when pushin the changes and tring to do:
$ heroku run rake db:migrate
the heroku answer where somthing like ->
Gem::LoadError: can't activate pg (~> 0.15), already activated pg-1.0.0. Make sure all dependencies are added to Gemfile.
It really frustates me and google it for a while.
I deleted the app and try it again, did not work.
I did some research and try on terminal from Heroku, tried to delete the pg and then install it again, did not work.
any wat tried some other solutions that came from google but did not work, and here is the solution
as you can see the pf gem needs to change in its definition dont really know why this happen but it seems that the problem arised on an updating rails from claud9 ide.