https://www.drupal.org/node/2709593

gistfile1.txt

m3:/data/disk/o8/aegir/distro/001/sites/o8.m3.s9.ams.boa.io# drush8 status
 Drupal version         :  7.43
 Site URI               :  http://o8.m3.s9.ams.boa.io
 Database driver        :  mysql
 Database hostname      :  localhost
 Database port          :  3306
 Database username      :  o8m3s9amsboaio
 Database name          :  o8m3s9amsboaio
 PHP executable         :  /usr/bin/php-cli
 PHP configuration      :  /opt/php56/lib/php.ini
 PHP OS                 :  Linux
 Drush script           :  /opt/tools/drush/8/drush/drush.php
 Drush version          :  8.1-dev
 Drush temp directory   :
 Drush configuration    :  /data/disk/o8/aegir/distro/001/sites/o8.m3.s9.ams.boa.io/drushrc.php
                           /data/disk/o8/aegir/distro/001/sites/all/drush/drushrc.php
 Drush alias files      :
 Drupal root            :  /data/disk/o8/aegir/distro/001
 Drupal Settings File   :  sites/o8.m3.s9.ams.boa.io/settings.php
 Site path              :  sites/o8.m3.s9.ams.boa.io


m3:/data/disk/o8/aegir/distro/001/sites/o8.m3.s9.ams.boa.io# drush7 status
Drush command terminated abnormally due to an unrecoverable error.                                                            [error]
Error: Call to undefined function provision_autoload_register_prefix() in
/data/disk/o8/aegir/distro/001/profiles/hostmaster/modules/aegir/hosting/example/example_service/drush/example.drush.inc,
line 29