...here is the diff:

=== modified file 'lib/lp/bugs/browser/tests/test_bugtask.py'
--- lib/lp/bugs/browser/tests/test_bugtask.py	2010-04-14 15:51:13 +0000
+++ lib/lp/bugs/browser/tests/test_bugtask.py	2010-04-15 10:38:07 +0000
@@ -217,10 +217,9 @@
 
     def setUp(self):
         super(TestBugTaskEditViewStatusField, self).setUp()
-        product_owner = self.factory.makePersonNoCommit(name='product-owner')
-        bug_supervisor = self.factory.makePersonNoCommit(
-            name='bug-supervisor')
-        product = self.factory.makeProductNoCommit(
+        product_owner = self.factory.makePerson(name='product-owner')
+        bug_supervisor = self.factory.makePerson(name='bug-supervisor')
+        product = self.factory.makeProduct(
             owner=product_owner, bug_supervisor=bug_supervisor)
         self.bug = self.factory.makeBug(product=product)
 

=== modified file 'lib/lp/bugs/interfaces/bugtask.py'
--- lib/lp/bugs/interfaces/bugtask.py	2010-04-14 13:23:02 +0000
+++ lib/lp/bugs/interfaces/bugtask.py	2010-04-15 13:08:31 +0000
@@ -317,6 +317,7 @@
 
 BUG_SUPERVISOR_BUGTASK_STATUSES = (
     BugTaskStatus.WONTFIX,
+    BugTaskStatus.EXPIRED,
     BugTaskStatus.TRIAGED)
 
 DEFAULT_SEARCH_BUGTASK_STATUSES = (

=== modified file 'lib/lp/bugs/tests/bugs-emailinterface.txt'
--- lib/lp/bugs/tests/bugs-emailinterface.txt	2009-08-13 15:12:16 +0000
+++ lib/lp/bugs/tests/bugs-emailinterface.txt	2010-04-15 14:00:55 +0000
@@ -1374,6 +1374,11 @@
     >>> print upstream_task.status.title
     Won't Fix
 
+    >>> submit_commands(bug_four, 'status expired')
+    >>> sync(upstream_task)
+    >>> print upstream_task.status.title
+    Expired
+
 Everyone else gets an explanatory error message:
 
     >>> from canonical.launchpad.interfaces import BugTaskStatus
@@ -1400,6 +1405,19 @@
     registrant or a bug supervisor for Mozilla Firefox.
     ...
 
+    >>> submit_commands(bug_four, 'affects firefox', 'status expired')
+    >>> print_latest_email()
+    Subject: Submit Request Failure
+    To: <email address hidden>
+    <BLANKLINE>
+    ...
+    Failing command:
+        status expired
+    ...
+    The status cannot be changed to expired because you are not the
+    registrant or a bug supervisor for Mozilla Firefox.
+    ...
+
 Let's take a look at all the other error messages that the sub
 commands can produce.
 
@@ -1417,7 +1435,7 @@
         status foo
     ...
     The 'status' command expects any of the following arguments:
-    new, incomplete, invalid, wontfix, confirmed, triaged, inprogress, fixcommitted, fixreleased
+    new, incomplete, invalid, wontfix, expired, confirmed, triaged, inprogress, fixcommitted, fixreleased
     <BLANKLINE>
     For example:
     <BLANKLINE>

=== modified file 'lib/lp/bugs/tests/bugtarget-bugcount.txt'
--- lib/lp/bugs/tests/bugtarget-bugcount.txt	2009-06-12 16:36:02 +0000
+++ lib/lp/bugs/tests/bugtarget-bugcount.txt	2010-04-15 11:46:39 +0000
@@ -13,6 +13,7 @@
     INCOMPLETE
     INVALID
     WONTFIX
+    EXPIRED
     CONFIRMED
     TRIAGED
     INPROGRESS
@@ -55,6 +56,7 @@
     INCOMPLETE: 5 bug(s) more
     INVALID: 5 bug(s) more
     WONTFIX: 5 bug(s) more
+    EXPIRED: 5 bug(s) more
     CONFIRMED: 5 bug(s) more
     TRIAGED: 5 bug(s) more
     INPROGRESS: 5 bug(s) more

=== modified file 'lib/lp/bugs/tests/test_bugtask_status.txt'
--- lib/lp/bugs/tests/test_bugtask_status.txt	2010-04-01 17:13:37 +0000
+++ lib/lp/bugs/tests/test_bugtask_status.txt	2010-04-15 13:18:45 +0000
@@ -13,8 +13,8 @@
     ...     nopriv_user, 'Test bug', 'Something')
     >>> firefox_bug = firefox.createBug(bug_params)
 
-Bug Supervisors can transition bugs to the Won't Fix and Triaged
-statuses.
+Bug Supervisors can transition bugs to the Won't Fix, Expired and
+Triaged statuses.
 
     >>> [firefox_bugtask] = firefox_bug.bugtasks
     >>> firefox_bugtask.transitionToStatus(
@@ -23,12 +23,17 @@
     Won't Fix
 
     >>> firefox_bugtask.transitionToStatus(
+    ...     BugTaskStatus.EXPIRED, nopriv_user)
+    >>> print firefox_bugtask.status.title
+    Expired
+
+    >>> firefox_bugtask.transitionToStatus(
     ...     BugTaskStatus.TRIAGED, nopriv_user)
     >>> print firefox_bugtask.status.title
     Triaged
 
-The product registrant can transition to the Won't Fix and Triaged
-statuses too.
+The product registrant can transition to the Won't Fix, Expired and
+Triaged statuses too.
 
     >>> firefox_bugtask.transitionToStatus(
     ...     BugTaskStatus.CONFIRMED, nopriv_user)
@@ -44,6 +49,11 @@
     Won't Fix
 
     >>> firefox_bugtask.transitionToStatus(
+    ...     BugTaskStatus.EXPIRED, firefox.owner)
+    >>> print firefox_bugtask.status.title
+    Expired
+
+    >>> firefox_bugtask.transitionToStatus(
     ...     BugTaskStatus.TRIAGED, firefox.owner)
     >>> print firefox_bugtask.status.title
     Triaged
@@ -65,6 +75,12 @@
     UserCannotEditBugTaskStatus: Only Bug Supervisors may change status to Won't Fix.
 
     >>> firefox_bugtask.transitionToStatus(
+    ...     BugTaskStatus.EXPIRED, nopriv_user)
+    Traceback (most recent call last):
+    ...
+    UserCannotEditBugTaskStatus: Only Bug Supervisors may change status to Expired.
+
+    >>> firefox_bugtask.transitionToStatus(
     ...     BugTaskStatus.TRIAGED, nopriv_user)
     Traceback (most recent call last):
     ...