現象

こんなエラーが出た。

Started GET "/users/auth/facebook/callback?redirect_uri=REDIRECT_URL&code=CODE&state=STATE" for ::1 at 2015-11-28 14:14:54 +0900
I, [2015-11-28T14:14:54.941266 #9383]  INFO -- omniauth: (facebook) Callback phase initiated.
E, [2015-11-28T14:14:56.362811 #9383] ERROR -- omniauth: (facebook) Authentication failure! invalid_credentials: OAuth2::Error, :
{"error":{"message":"Error validating verification code. Please make sure your redirect_uri is identical to the one you used in the OAuth dialog request","type":"OAuthException","code":100,"fbtrace_id":"FACEBOOK_ID"}}
Processing by Users::OmniauthCallbacksController#failure as HTML
  Parameters: {"redirect_uri"=>"http://localhost:3000//", "code"=>"CODE", "state"=>"STATE"}
Redirected to http://localhost:3000/users/sign_in
Completed 302 Found in 88ms (ActiveRecord: 0.0ms)

対策

deviseのwikiを見ると

Note: v2.0.1 has an issue with callback url error. You need to add a callback url on config.

config.omniauth :facebook, "APP_ID", "APP_SECRET",
                callback_url: "CALLBACK_URL"

バージョン固有の問題かもしれない。
omniauth-facebookのバージョンをみると

omniauth-facebook (2.0.1)

バージョンにこだわりはなかったので、バージョンを上げてしまうことにする。

bundle update omniauth-facebook

解決した。