uninitialized constant OmniAuth

[jeffingo]

Hello

i was trying to run bundle && bundle exec rails g spree_social:install

but i get this error below , kindly assist
<module:Strategies>': uninitialized constant OmniAuth::Strategies::OAuth2 (NameError) from /home/jeffingo/Downloads/spree_social/lib/spree_social/engine.rb:49:inmodule:OmniAuth'
from /home/jeffingo/Downloads/spree_social/lib/spree_social/engine.rb:48:in <top (required)>' from /home/jeffingo/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/railties-4.2.0/lib/rails/engine/commands.rb:11:inrequire'
from /home/jeffingo/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/railties-4.2.0/lib/rails/engine/commands.rb:11:in <top (required)>' from bin/rails:7:inrequire'
from bin/rails:7:in `

'