PostgreSQL: fix transaction bug that can occur if you call change_column with invalid parameters

[#861 state:resolved]

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -761,7 +761,8 @@ module ActiveRecord
 
         begin
           execute "ALTER TABLE #{quoted_table_name} ALTER COLUMN #{quote_column_name(column_name)} TYPE #{type_to_sql(type, options[:limit], options[:precision], options[:scale])}"
-        rescue ActiveRecord::StatementInvalid
+        rescue ActiveRecord::StatementInvalid => e
+          raise e if postgresql_version > 80000
           # This is PostgreSQL 7.x, so we have to use a more arcane way of doing it.
           begin
             begin_db_transaction