Add warning about failed LE certificates obtaining to domains list

+ view specs

app/views/projects/pages/_list.html.haml

@@ -30,3 +30,10 @@
             = s_('GitLabPages|%{domain} is not verified. To learn how to verify ownership, visit your %{link_start}domain details%{link_end}.').html_safe % { domain: domain.domain,
                 link_start: details_link_start,
                 link_end: details_link_end }
+        - elsif ::Gitlab::LetsEncrypt.enabled? && domain.auto_ssl_failed && Feature.enabled?(:pages_letsencrypt_errors, @project)
+          %li.list-group-item.bs-callout-warning
+            - details_link_start = "<a href='#{project_pages_domain_path(@project, domain)}'>".html_safe
+            - details_link_end = '</a>'.html_safe
+            = s_("GitLabPages|Something went wrong while obtaining Let's Encrypt certificate for %{domain}. To retry visit your %{link_start}domain details%{link_end}.").html_safe % { domain: domain.domain,
+                link_start: details_link_start,
+                link_end: details_link_end }

locale/gitlab.pot

@@ -9723,6 +9723,9 @@ msgstr ""
 msgid "GitLabPages|Save"
 msgstr ""
 
+msgid "GitLabPages|Something went wrong while obtaining Let's Encrypt certificate for %{domain}. To retry visit your %{link_start}domain details%{link_end}."
+msgstr ""
+
 msgid "GitLabPages|Support for domains and certificates is disabled.  Ask your system's administrator to enable it."
 msgstr ""
 

spec/views/projects/pages/show.html.haml_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe 'projects/pages/show' do
+  include LetsEncryptHelpers
+
+  let(:project) { create(:project, :repository) }
+  let(:user) { create(:user) }
+  let(:domain) { create(:pages_domain, project: project) }
+  let(:error_message) do
+    "Something went wrong while obtaining Let's Encrypt certificate for #{domain.domain}. "\
+    "To retry visit your domain details."
+  end
+
+  before do
+    allow(project).to receive(:pages_deployed?).and_return(true)
+    stub_pages_setting(external_https: true)
+    stub_lets_encrypt_settings
+    project.add_maintainer(user)
+
+    assign(:project, project)
+    allow(view).to receive(:current_user).and_return(user)
+    assign(:domains, [domain])
+  end
+
+  it "doesn't show auto ssl error warning" do
+    render
+
+    expect(rendered).not_to have_content(error_message)
+  end
+
+  context "when we failed to obtain Let's Encrypt's certificate" do
+    before do
+      domain.update!(auto_ssl_failed: true)
+    end
+
+    it 'shows auto ssl error warning' do
+      render
+
+      expect(rendered).to have_content(error_message)
+    end
+
+    it "doesn't show warning if lets_encrypt_error feature flag is disabled" do
+      stub_feature_flags(pages_letsencrypt_errors: false)
+
+      render
+
+      expect(rendered).not_to have_content(error_message)
+    end
+
+    it "doesn't show warning if Let's Encrypt integration is disabled" do
+      allow(::Gitlab::LetsEncrypt).to receive(:enabled?).and_return false
+
+      render
+
+      expect(rendered).not_to have_content(error_message)
+    end
+  end
+end