Refactor and translate PostgreSQL version warning

The refactor preceded some code reuse in an earlier iteration of
https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/8433
but is now just a small standalone improvement.

ee/app/controllers/admin/geo/nodes_controller.rb

@@ -12,7 +12,11 @@ class Admin::Geo::NodesController < Admin::ApplicationController
     @node = GeoNode.new
 
     unless Gitlab::Geo.license_allows?
-      flash_now(:alert, 'You need a different license to enable Geo replication')
+      flash.now[:alert] = _('You need a different license to enable Geo replication.')
+    end
+
+    unless Gitlab::Database.pg_stat_wal_receiver_supported?
+      flash.now[:warning] = _('Please upgrade PostgreSQL to version 9.6 or greater. The status of the replication cannot be determined reliably with the current version.')
     end
   end
   # rubocop: enable CodeReuse/ActiveRecord
@@ -67,8 +71,4 @@ class Admin::Geo::NodesController < Admin::ApplicationController
   def load_node
     @node = GeoNode.find(params[:id])
   end
-
-  def flash_now(type, message)
-    flash.now[type] = flash.now[type].blank? ? message : "#{flash.now[type]}<BR>#{message}".html_safe
-  end
 end

ee/app/views/admin/geo/nodes/index.html.haml

@@ -12,10 +12,6 @@
 %p.page-subtitle.light
   = s_('GeoNodes|With %{geo} you can install a special read-only and replicated instance anywhere. Before you add nodes, follow the %{instructions} in the exact order they appear.').html_safe % { geo: link_to('GitLab Geo', help_page_path('administration/geo/replication/index.md'), target: '_blank'), instructions: link_to('setup instructions', help_page_path('administration/geo/replication/index.md', anchor: 'setup-instructions'), target: '_blank') }
 
-- unless Gitlab::Database.pg_stat_wal_receiver_supported?
-  = content_for :flash_message do
-    .alert.alert-warning WARNING: Please upgrade PostgreSQL to version 9.6 or greater. The status of the replication cannot be determined reliably with the current version.
-
 - if @nodes.any?
   #js-geo-nodes{ data: node_vue_list_properties }
 - else

ee/spec/controllers/admin/geo/nodes_controller_spec.rb

@@ -22,6 +22,22 @@ describe Admin::Geo::NodesController, :postgresql do
   describe '#index' do
     render_views
 
+    shared_examples 'no flash message' do |flash_type|
+      it 'does not display a flash message' do
+        go
+
+        expect(flash).not_to include(flash_type)
+      end
+    end
+
+    shared_examples 'with flash message' do |flash_type, message|
+      it 'displays a flash message' do
+        go
+
+        expect(flash[flash_type]).to match(message)
+      end
+    end
+
     def go
       get :index
     end
@@ -31,11 +47,7 @@ describe Admin::Geo::NodesController, :postgresql do
         allow(Gitlab::Geo).to receive(:license_allows?).and_return(true)
       end
 
-      it 'does not display a flash message' do
-        go
-
-        expect(flash).not_to include(:alert)
-      end
+      it_behaves_like 'no flash message', :alert
     end
 
     context 'without add-on license available' do
@@ -43,17 +55,29 @@ describe Admin::Geo::NodesController, :postgresql do
         allow(Gitlab::Geo).to receive(:license_allows?).and_return(false)
       end
 
-      it 'displays a flash message' do
-        go
-
-        expect(flash[:alert]).to include('You need a different license to enable Geo replication')
-      end
+      it_behaves_like 'with flash message', :alert, 'You need a different license to enable Geo replication'
 
       it 'does not redirects to the license page' do
         go
         expect(response).not_to redirect_to(admin_license_path)
       end
     end
+
+    context 'with Postgres 9.6 or greater' do
+      before do
+        allow(Gitlab::Database).to receive(:pg_stat_wal_receiver_supported?).and_return(true)
+      end
+
+      it_behaves_like 'no flash message', :warning
+    end
+
+    context 'without Postgres 9.6 or greater' do
+      before do
+        allow(Gitlab::Database).to receive(:pg_stat_wal_receiver_supported?).and_return(false)
+      end
+
+      it_behaves_like 'with flash message', :warning, 'Please upgrade PostgreSQL to version 9.6 or greater.'
+    end
   end
 
   describe '#create' do

locale/gitlab.pot

@@ -6596,6 +6596,9 @@ msgstr ""
 msgid "Please try again"
 msgstr ""
 
+msgid "Please upgrade PostgreSQL to version 9.6 or greater. The status of the replication cannot be determined reliably with the current version."
+msgstr ""
+
 msgid "Please use this form to report users to GitLab who create spam issues, comments or behave inappropriately."
 msgstr ""
 
@@ -10194,6 +10197,9 @@ msgstr ""
 msgid "You need a different license to enable FileLocks feature"
 msgstr ""
 
+msgid "You need a different license to enable Geo replication."
+msgstr ""
+
 msgid "You need git-lfs version %{min_git_lfs_version} (or greater) to continue. Please visit https://git-lfs.github.com"
 msgstr ""