Rails controller rescue exception in `lib` directory - ruby-on-rails

Question

I'm using a wrapper around a Wikipedia OmniAuth gem in my Devise initializer that is periodically throwing JWT::DecodeErrors. I'm trying to handle these errors with a custom error message, rather than throwing a 500. (Stick with me here.)
In my Devise initializer, I set up the strategy as such:
config.omniauth :mediawiki,
Figaro.env.wikipedia_token,
Figaro.env.wikipedia_secret,
strategy_class: CustomStrategy,
client_options: {
site: "https://#{Figaro.env.wiki_language}.wikipedia.org"
}
My CustomStrategy inherits from the default MediaWiki strategy and adds some data to the request object to check for it later in the ErrorsController:
# lib/custom_strategy.rb
class LoginError < StandardError; end
class CustomStrategy < OmniAuth::Strategies::Mediawiki
def parse_info(jwt_data)
begin
super
rescue JWT::DecodeError
request.env['JWT_ERROR'] = true
request.env['JWT_DATA'] = jwt_data
raise ::LoginError.new("\nA JWT::DecodeError occurred. Here is the web token data:\n#{jwt_data.body.inspect}")
end
end
end
So here I try to catch the JWT::DecodeError by raising a LoginError that I'm hoping to catch in my controller:
class ApplicationController < ActionController::Base
rescue_from StandardError, with: :handle_login_error
...
protected
def handle_login_error
redirect_to errors_login_error_path
end
end
The problem is that rescue_from only handles exceptions thrown in the controller.
Since this exception is thrown in my strategy, I don't have the opportunity to rescue it, and Rails just treats it as a 500:
[2016-01-26 12:10:02.183 FATAL] StandardError (
A JWT::DecodeError occurred. Here is the web token data:
"{\"error\":\"mwoauthdatastore-access-token-not-found\",\"message\":\"No approved grant was found for that authorization token.\"}"):
lib/custom_strategy.rb:9:in `rescue in parse_info'
lib/custom_strategy.rb:6:in `parse_info'
[2016-01-26 12:10:02.251 INFO ] Processing by ErrorsController#internal_server_error as HTML
[2016-01-26 12:10:02.251 INFO ] Parameters: {"oauth_verifier"=>"XXXXXXXXXXXXXXXX", "oauth_token"=>"XXXXXXXXXXXXXXX"}
[2016-01-26 12:10:02.971 INFO ] Rendered errors/internal_server_error.html.erb within layouts/application (3.8ms)
[2016-01-26 12:10:03.204 INFO ] Rendered shared/_head.html.haml (10.1ms)
[2016-01-26 12:10:03.215 INFO ] Rendered shared/_nav.html.haml (9.7ms)
[2016-01-26 12:10:03.218 INFO ] Rendered shared/_foot.html.haml (2.3ms)
[2016-01-26 12:10:03.219 INFO ] Completed 500 Internal Server Error in 967ms (Views: 265.8ms | ActiveRecord: 0.0ms)
So here, Rails treats it as a 500, and I'm using custom error pages, not the Rails defaults.
For reference, here's my ErrorsController:
class ErrorsController < ApplicationController
respond_to :html, :json
def file_not_found
render status: 404
end
def unprocessable
render status: 422
end
def internal_server_error
if request.env['JWT_ERROR']
return login_error
end
render status: 500
end
def incorrect_passcode
render status: 401
end
def login_error
#return render status: 599
end
end
What's the best way to handle this exception that happens in the jwt-ruby gem, which is a dependency of the oauth-mediawiki gem that I'm wrapping with a custom strategy that hopes to catch the JWT::DecodeError and handle it within my app? If this specific error arises, I want to render a special view, not just the 500 view.
Edit 2: Further Articulation of the Problem
The problem is that I can't figure out a way to rescue the exception I've rescued and re-raised (JWT::DecodeError) in a way that allows me to render a custom view. As you can see from the log above, it just renders ErrorsContoller#internal_server_error.