Use older version of Rake
gem search (or list) rake, should tell you which versions are installed.
You can invoke rake with a specific version number bracketed withunderscores.
$rake _0.7.3_
This is a standard feature of gem packaged binaries.
You can specify the version of Rake to use, in your Gemfile:
gem 'rake', '0.8.7'
Though the "error" message you are getting says it all... you need to run:
bundle exec rake ...
... in order to use the right rake to run your rake tasks.
More info on bundle exec
: http://gembundler.com/man/bundle-exec.1.html
Try executing gem uninstall rake
then just pick the version you want to uninstall.