Request#check_method no longer breaks when :en is not available locale

Request#check_method would use to_sentence(locale: :en), which breaks when
I18n.available_locales does not include :en and
I18n.enforce_available_locales is true (default).

Inlined to_sentence functionality to solve this.

actionpack/lib/action_dispatch/http/request.rb

@@ -341,7 +341,7 @@ module ActionDispatch
 
     private
       def check_method(name)
-        HTTP_METHOD_LOOKUP[name] || raise(ActionController::UnknownHttpMethod, "#{name}, accepted HTTP methods are #{HTTP_METHODS.to_sentence(:locale => :en)}")
+        HTTP_METHOD_LOOKUP[name] || raise(ActionController::UnknownHttpMethod, "#{name}, accepted HTTP methods are #{HTTP_METHODS[0...-1].join(', ')}, and #{HTTP_METHODS[-1]}")
         name
       end
   end

actionpack/test/dispatch/request_test.rb

@@ -683,6 +683,22 @@ class RequestMethod < BaseRequestTest
     end
   end
 
+  test "exception on invalid HTTP method unaffected by I18n settings" do
+    old_locales = I18n.available_locales
+    old_enforce = I18n.config.enforce_available_locales
+
+    begin
+      I18n.available_locales = [:nl]
+      I18n.config.enforce_available_locales = true
+      assert_raise(ActionController::UnknownHttpMethod) do
+        stub_request('REQUEST_METHOD' => '_RANDOM_METHOD').method
+      end
+    ensure
+      I18n.available_locales = old_locales
+      I18n.config.enforce_available_locales = old_enforce
+    end
+  end
+
   test "post masquerading as patch" do
     request = stub_request(
       'REQUEST_METHOD' => 'PATCH',