Refactor fail callbacks in list import controller

[MAILPOET-1732]

assets/js/src/wizard/woocommerce_import_controller.jsx

@@ -25,15 +25,7 @@ class WooCommerceImportController extends React.Component {
       endpoint: 'settings',
       action: 'set',
       data,
-    }).fail((response) => {
+    }).fail(this.handleApiError);
-      this.setState({ loading: false });
-      if (response.errors.length > 0) {
-        MailPoet.Notice.error(
-          response.errors.map(error => error.message),
-          { scroll: true }
-        );
-      }
-    });
   }
 
   scheduleImport() {
@@ -41,15 +33,16 @@ class WooCommerceImportController extends React.Component {
       api_version: window.mailpoet_api_version,
       endpoint: 'importExport',
       action: 'setupWooCommerceInitialImport',
-    }).then(() => this.setState({ loading: false })).fail((response) => {
+    }).then(() => this.setState({ loading: false })).fail(this.handleApiError);
-      this.setState({ loading: false });
+  }
-      if (response.errors.length > 0) {
+
-        MailPoet.Notice.error(
+  handleApiError(response) {
-          response.errors.map(error => error.message),
+    this.setState({ loading: false });
-          { scroll: true }
+    let errorMessage = MailPoet.I18n.t('unknownError');
-        );
+    if (response && response.errors && response.errors.length > 0) {
-      }
+      errorMessage = response.errors.map(error => error.message);
-    });
+    }
+    MailPoet.Notice.error(errorMessage, { scroll: true });
   }
 
   submit(importType) {

views/woocommerce_list_import.html

@@ -20,5 +20,6 @@
 'wooCommerceListImportCheckboxUnsubscribed': __('<b>add</b> all my customers to the list, but <b>as unsubscribed</b>. They can join this list next time they check out'),
 'wooCommerceListImportInfo4': __('Their subscription preference on other lists won’t be changed.'),
 'wooCommerceListImportSubmit': _x('Create my WooCommerce Customers list now!', 'Submit button caption'),
+'unknownError': __('Unknown error'),
 }) %>
 <% endblock %>