Remove rackmount const usage

actionpack/lib/action_dispatch/routing/mapper.rb

@@ -195,9 +195,9 @@ def call(env)
 
           @constraints.each { |constraint|
             if constraint.respond_to?(:matches?) && !constraint.matches?(req)
-              return Rack::Mount::Const::EXPECTATION_FAILED_RESPONSE
+              return [417, {}, []]
             elsif constraint.respond_to?(:call) && !constraint.call(req)
-              return Rack::Mount::Const::EXPECTATION_FAILED_RESPONSE
+              return [417, {}, []]
             end
           }
 

actionpack/lib/action_dispatch/routing/route_set.rb

@@ -5,7 +5,7 @@ module ActionDispatch
   module Routing
     class RouteSet #:nodoc:
       NotFound = lambda { |env|
-        raise ActionController::RoutingError, "No route matches #{env[::Rack::Mount::Const::PATH_INFO].inspect} with #{env.inspect}"
+        raise ActionController::RoutingError, "No route matches #{env['PATH_INFO'].inspect} with #{env.inspect}"
       }
 
       PARAMETERS_KEY = 'action_dispatch.request.path_parameters'