title: Drush command terminated abnormally due to an unrecoverable error
body: <p>I have CentOS 6.6 with PHP 5.5.27 and Drupal 7.34</p>
  
  <pre><code>PHP 5.5.27 (cli) (built: Jul 10 2015 23:40:40)
  Copyright (c) 1997-2015 The PHP Group
  Zend Engine v2.5.0, Copyright (c) 1998-2015 Zend Technologies
  </code></pre>
  
  <p>I've tried all latest 6,7,8 branches of Drush. When I type "drush -d -v status" I get an unrecoverable error (the error is the same on all branches of drush):</p>
  
  <pre><code>Drush bootstrap phase : bootstrap_drupal_full() [0.19 sec, 5.13 MB]                                           [bootstrap]
  Cannot modify header information - headers already sent by (output started at                                 [warning]
  /root/.composer/vendor/drush/drush/includes/output.inc:38) common.inc:698 [0.96 sec, 31.89 МБ]
  Drush command terminated abnormally due to an unrecoverable error. [1.06 sec, 32.8 МБ]              
  </code></pre>
  
  <p>I can't figure out what's wrong. Can anyone advise please?</p>
  
  <p>Thanks in advance.</p>