Description of problem:
1- subscribe to a list
2- click on the link provided in the confirmation email
3- click "cancel my subscription request"

Version-Release number of selected component (if applicable):
mailman-2.1.5-24.rhel3

How reproducible:
verified on ppc, ia64, and i386.
  
Actual results:
Bug in Mailman version 2.1.5

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Traceback:

Traceback (most recent call last):
  File "/var/mailman/scripts/driver", line 87, in run_main
    main()
  File "/var/mailman/Mailman/Cgi/confirm.py", line 114, in main
    subscription_cancel(mlist, doc, cookie)
  File "/var/mailman/Mailman/Cgi/confirm.py", line 312, in subscription_cancel
    userdesc = mlist.pend_confirm(cookie)[1]
  File "/var/mailman/Mailman/Pending.py", line 141, in pend_confirm
    assert self.Locked()
AssertionError

Python information:

Variable	Value
sys.version	2.2.3 (#1, Feb 2 2005, 12:38:05) [GCC 3.2.3 20030502 (Red Hat Linux
3.2.3-49)]
sys.executable	/usr/bin/python
sys.prefix	/usr
sys.exec_prefix	/usr
sys.path	/usr
sys.platform	linux2

Environment variables:

Variable	Value
PATH_INFO 	/before-upgrade
CONTENT_LENGTH 	117
CONTENT_TYPE 	application/x-www-form-urlencoded
HTTP_COOKIE 
after-upgrade+admin=280200000069361c3b42732800000039636337663261393232623937306665313733626332396135646235393638333665326666383431;
before-upgrade+admin=2802000000699a483b42732800000032613938633738386439333864333663336230613734306632313533663338636639323361636136;
rh_auth_token=578122:1111098369xa884818741fab532682b5755df4da015
SCRIPT_FILENAME 	/var/mailman/cgi-bin/confirm
PYTHONPATH 	/var/mailman
SERVER_SOFTWARE 	Apache/2.0.46 (Red Hat)
SERVER_ADMIN 	root@localhost
SCRIPT_NAME 	/mailman/confirm
SERVER_SIGNATURE 	
Apache/2.0.46 (Red Hat) Server at server.redhat.com Port 80
REQUEST_METHOD 	POST
HTTP_HOST 	server.redhat.com
HTTP_KEEP_ALIVE 	300
SERVER_PROTOCOL 	HTTP/1.1
QUERY_STRING 	
PATH_TRANSLATED 	/var/www/html/before-upgrade
REQUEST_URI 	/mailman/confirm/before-upgrade
HTTP_ACCEPT 
text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
HTTP_ACCEPT_CHARSET 	ISO-8859-1,utf-8;q=0.7,*;q=0.7
HTTP_USER_AGENT 	Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.5)
Gecko/20041216 Firefox/1.0 Red Hat/1.0-13.EL4
HTTP_CONNECTION 	keep-alive
HTTP_REFERER 
http://server.redhat.com/mailman/confirm/before-upgrade/0645ebf93a9ebc8519f1abc5c3046c88cb921e7a
SERVER_NAME 	server.redhat.com
REMOTE_ADDR 	1XX.XX.XX.XX
REMOTE_PORT 	45908
HTTP_ACCEPT_LANGUAGE 	en-us,en;q=0.5
UNIQUE_ID 	JETCCMCoIJcAAAb8kyQAAAAC
SERVER_PORT 	80
GATEWAY_INTERFACE 	CGI/1.1
HTTP_ACCEPT_ENCODING 	gzip,deflate
SERVER_ADDR 	1XX.XXX.XX.XXX
DOCUMENT_ROOT 	/var/www/html