Change record status: 
Project: 
Introduced in branch: 
8.x
Description: 

When you deal with the new config system (see https://drupal.org/node/1500260 for more information), you should access properties with \Drupal::config(), rather then config(), which is deprecated.

Before:

<?php
$gzip
= config('system.performance')->get('response.gzip');
?>

After:
<?php
$gzip
= \Drupal::config('system.performance')->get('response.gzip');
?>

Note also that in a class you should inject the 'config.factory' service and get the config object from there

<?php
class {
  public function
__construct(ConfigFactory $config_factory) {
   
$this->config = $config_factory->get('system.performance');
  }
  public function
other() {
   
$gzip = $this->config->get('response.gzip');
  }
}
?>
Impacts: 
Module developers
Updates Done (doc team, etc.)
Online documentation: 
Not done
Theming guide: 
Not done
Module developer documentation: 
Not done
Examples project: 
Not done
Coder Review: 
Not done
Coder Upgrade: 
Not done
Other: 
Other updates done