Catch OIDC error

app/controllers/admin/dfc_product_imports_controller.rb

@@ -10,7 +10,7 @@
       self.class
     end
 
     def index
       # The plan:
       #
       # * Fetch DFC catalog as JSON from URL.
@@ -35,6 +35,15 @@
       end
 
       @count = imported.compact.count
+    rescue Rack::OAuth2::Client::Error => e
+      flash[:error] = I18n.t(
+        'admin.dfc_product_imports.index.oauth_error_html',
+        message: e.message,
+        oidc_settings_link: ActionController::Base.helpers.link_to(
+          I18n.t('spree.admin.tab.oidc_settings'), Rails.application.routes.url_helpers.admin_oidc_settings_path
+        )
+      ).html_safe
+      redirect_to admin_product_import_path
     rescue Faraday::Error,
            Addressable::URI::InvalidURIError,
            ActionController::ParameterMissing => e

config/locales/en.yml

@@ -849,6 +849,7 @@ en:
       index:
         title: "Importing a DFC product catalog"
         imported_products: "Imported products:"
+        oauth_error_html: "Authentication error: %{message}. See %{oidc_settings_link}"
     enterprise_fees:
       index:
         title: "Enterprise Fees"

spec/system/admin/dfc_product_import_spec.rb

@@ -74,6 +74,30 @@
     expect(product.image).to be_present
   end
 
+  it "shows oauth error message", vcr: true do
+    allow_any_instance_of(DfcRequest).to receive(:refresh_access_token!).and_raise(
+      Rack::OAuth2::Client::Error.new(
+        1, { error: "invalid_grant", error_description: "session not active" }
+      )
+    )
+
+    user.update!(oidc_account: build(:testdfc_account))
+
+    visit admin_product_import_path
+
+    select enterprise.name, from: "Enterprise"
+    url = "https://env-0105831.jcloud-ver-jpe.ik-server.com/api/dfc/Enterprises/test-hodmedod/SuppliedProducts"
+    fill_in "catalog_url", with: url
+
+    click_button "Import"
+
+    within ".flash" do
+      expect(page).to have_content "invalid_grant"
+      expect(page).to have_content "session not active"
+      expect(page).to have_link "OIDC Settings"
+    end
+  end
+
   it "fails gracefully" do
     user.oidc_account.update!(
       uid: "anonymous@example.net",