mailman @2.1.22_0: ImportError: cannot import name C_

[KiyoshiGotow]

I have tried to update mailman from 2.1.20_0 to 2.1.22_0, and got an error message as follows.

The current version of mailman on my system is 2.1.20_0, and it seems to work fine. The version of python is 2.7.11_2.

$ sudo port clean mailman
Password:
--->  Cleaning mailman
$ sudo port upgrade mailman
--->  Computing dependencies for mailman
--->  Fetching archive for mailman
--->  Attempting to fetch mailman-2.1.22_0.darwin_12.x86_64.tbz2 from http://sea.us.packages.macports.org/macports/packages/mailman
--->  Attempting to fetch mailman-2.1.22_0.darwin_12.x86_64.tbz2 from https://packages.macports.org/mailman
--->  Attempting to fetch mailman-2.1.22_0.darwin_12.x86_64.tbz2 from http://mse.uk.packages.macports.org/sites/packages.macports.org/mailman
      [                                        ]   0.0 %        speed: 0 B/s        --->  Fetching distfiles for mailman
--->  Verifying checksums for mailman
--->  Extracting mailman
--->  Applying patches to mailman
--->  Configuring mailman
--->  Building mailman
--->  Staging mailman into destroot
Error: org.macports.destroot for port mailman returned: command execution failed
Please see the log file for port mailman for details:
    /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_mail_mailman/mailman/main.log
Error: Unable to upgrade port: 1
To report a bug, follow the instructions in the guide:
    http://guide.macports.org/#project.tickets

[ryandesign (Ryan Carsten Schmidt)]

Relevant error from log appears to be:

:info:destroot Traceback (most recent call last):
:info:destroot   File "./bin/check_perms", line 48, in <module>
:info:destroot     from Mailman.i18n import C_
:info:destroot ImportError: cannot import name C_