This class handles installing and switching to the version of bundler needed by an application.
# File bundler/self_manager.rb, line 15
def install_locked_bundler_and_restart_with_it_if_needed
return unless needs_switching?
Bundler.ui.info \
"Bundler #{current_version} is running, but your lockfile was generated with #{lockfile_version}. " \
"Installing Bundler #{lockfile_version} and restarting using that version."
install_and_restart_with_locked_bundler
end