Fix pg extension creation in migration for #1097

db/migrate/20180108132507_enable_unaccent_postgresql_extension.rb

@@ -1,9 +1,9 @@
 class EnableUnaccentPostgresqlExtension < ActiveRecord::Migration[5.0]
   def up
-    execute 'CREATE EXTENSION unaccent;'
+    execute 'CREATE EXTENSION IF NOT EXISTS unaccent;'
   end
 
   def down
-    execute 'DROP EXTENSION unaccent;'
+    execute 'DROP EXTENSION IF EXISTS unaccent;'
   end
 end