[Pkg-mailman-hackers] Bug#523554: Migration to not shipping /var/lock/mailman breaks mailman/bin/update call in postinst

[Max Bowsher]

Package: mailman
Version: 1:2.1.12-1
Severity: mailman

Upgrading to mailman 2.1.12-1 (the first version to stop shipping an actual
/var/lock/mailman directory in the package), the postinst emits the following
error:

Upgrading from version 0x2010bf0 to 0x2010cf0  
getting rid of old source files
Updating mailing list: mylist
Traceback (most recent call last):
  File "/usr/lib/mailman/bin/update", line 766, in <module>
    errors = main()
  File "/usr/lib/mailman/bin/update", line 656, in main
    errors = errors + dolist(listname)
  File "/usr/lib/mailman/bin/update", line 193, in dolist
    mlist.Lock(0.5)
  File "/var/lib/mailman/Mailman/MailList.py", line 161, in Lock
    self.__lock.lock(timeout)
  File "/var/lib/mailman/Mailman/LockFile.py", line 243, in lock
    self.__write()
  File "/var/lib/mailman/Mailman/LockFile.py", line 422, in __write
    fp = open(self.__tmpfname, 'w')
IOError: [Errno 2] No such file or directory: '/var/lib/mailman/locks/mylist.lock.sanpietro.16648.0'

The missing locks directory will later be created by the init.d script, but
this is too late for the update invoked earlier in the postinst.

The postinst does not error out, however, see bug #513988.