Role added to account: invalid token included in log text

In _role_watchdog_add_role():

$vars = array(
  'body' => 'Role !role!role_modifier added to !account by !user',
  // ...
);

!role_modifier is never given a replacement value, so the first part of it—!role—is replaced, while the '_modifier' stays on the end.

So, if I add a role called "editor," the resulting message is:

Role editoreditor_modifier added to account by user