Can't install Devise

same problem today, I removed the 'spring' out from the Gemfile and it did the trick. or you can turn off your spring first and run rails generate devise:install

OK, I'm still not 100% sure why this worked or what caused the issue in the first place but after running the following commands:

leigh@leigh-VirtualBox:~/Projects/dev01$ gem uninstall devise
Successfully uninstalled devise-3.2.4
leigh@leigh-VirtualBox:~/Projects/dev01$ gem uninstall warden
Successfully uninstalled warden-1.2.3
leigh@leigh-VirtualBox:~/Projects/dev01$ bundle install
Fetching gem metadata from https://rubygems.org/.........
Fetching additional metadata from https://rubygems.org/..
[... text removed ...]
Installing warden 1.2.3
Installing devise 3.2.4
[... text removed ...]
Your bundle is complete!
Use `bundle show [gemname]` to see where a bundled gem is installed.
leigh@leigh-VirtualBox:~/Projects/dev01$ rails generate devise:install
      create  config/initializers/devise.rb
      create  config/locales/devise.en.yml

Woo Hoo!!! problem solved. Great way to waste a couple of days :-(

What worked for me was:

$ sudo -s
$ bundle exec rails generate devise:install

Without sudo or running the "initializer" /bin/bash --login didn't work. The other solution could be to remove the Gemfile.lock and run bundle install again.