When trying to run `Drush pm-update' in a site i get the error
Command pm-update needs the following modules installed/enabled to run: update. [error] The drush command 'pm-update' could not be executed.
Oddly this command was recently working (on other sites in the same core installation), and further more I have no idea where to find or what is this 'update' module. Can anyone point me in the right direction?