Attempt to create pg_trgm extension in migration for test/dev environments

Closes #15210

db/migrate/20160226114608_add_trigram_indexes_for_searching.rb

@@ -4,6 +4,8 @@ class AddTrigramIndexesForSearching < ActiveRecord::Migration
   def up
     return unless Gitlab::Database.postgresql?
 
+    create_trigrams_extension
+
     unless trigrams_enabled?
       raise 'You must enable the pg_trgm extension. You can do so by running ' \
         '"CREATE EXTENSION pg_trgm;" as a PostgreSQL super user, this must be ' \
@@ -37,6 +39,15 @@ class AddTrigramIndexesForSearching < ActiveRecord::Migration
     row && row['enabled'] == 't' ? true : false
   end
 
+  def create_trigrams_extension
+    # This may not work if the user doesn't have permission. We attempt in
+    # case we do have permission, particularly for test/dev environments.
+    begin
+      enable_extension 'pg_trgm'
+    rescue
+    end
+  end
+
   def to_index
     {
       ci_runners:     [:token, :description],