Can't complete delete ueberauth_github

I used ueberauth_github in my project, then I delete everything about that. But when I run ‘MIX_ENV=prod PORT=8000 mix phoenix.server’ :

22:08:33.913 [info] Application postgrex exited: :stopped
22:08:33.913 [info] Application db_connection exited: :stopped
22:08:33.913 [info] Application connection exited: :stopped
22:08:33.913 [info] Application phoenix_ecto exited: :stopped
22:08:33.913 [info] Application ecto exited: :stopped
22:08:33.913 [info] Application poolboy exited: :stopped
22:08:33.913 [info] Application decimal exited: :stopped
22:08:33.913 [info] Application gettext exited: :stopped
22:08:33.913 [info] Application cowboy exited: :stopped
22:08:33.913 [info] Application cowlib exited: :stopped
22:08:33.913 [info] Application ranch exited: :stopped
22:08:33.913 [info] Application phoenix_html exited: :stopped
22:08:33.913 [info] Application phoenix_pubsub exited: :stopped
22:08:33.915 [info] Application phoenix exited: :stopped
22:08:33.916 [info] Application eex exited: :stopped
22:08:33.916 [info] Application poison exited: :stopped
22:08:33.917 [info] Application plug exited: :stopped
22:08:33.917 [info] Application mime exited: :stopped

=INFO REPORT==== 29-Oct-2016::22:08:33 ===
    application: logger
    exited: stopped
    type: permanent
** (Mix) Could not start application ueberauth_github: could not find application file: ueberauth_github.app

I searched ‘ueberauth’ in the entire project, nothing was found. How can I complete delete ueberauth_github?

Have you tried deleting _build?

Works for me, thank you!