Drush up : Command pm-update needs a higher bootstrap level to run

Command pm-update needs a higher bootstrap level to run - you will need to invoke drush from a more     [error]

functional Drupal environment to run this command.

The drush command 'up' could not be executed.                                                           [error]

Drush was not able to start (bootstrap) the Drupal database.                                            [error]

Hint: This may occur when Drush is trying to:

 * bootstrap a site that has not been installed or does not have a configured database. In this case you

can select another site with a working database setup by specifying the URI to use with the --uri

parameter on the command line. See `drush topic docs-aliases` for details.

 * connect the database through a socket. The socket file may be wrong or the php-cli may have no access

to it in a jailed shell. See http://drupal.org/node/1428638 for details.