Regression: syncing packages with UTF-8 changelogs fails

lp_archive@cocoplum:~/syncs$ sync-source.py -b cjwatson -S experimental dctrl-tools
Getting binaries for maverick...
[Updating] dctrl-tools (2.14 [Ubuntu] < 2.15 [Debian])
 * Trying to add dctrl-tools...
2010-09-11 07:53:51 INFO - <dctrl-tools_2.15.tar.gz: downloading from http://ftp.debian.org/debian/>
2010-09-11 07:53:51 INFO - <dctrl-tools_2.15.dsc: downloading from http://ftp.debian.org/debian/>
I: dctrl-tools [main] -> dctrl-tools_2.14 [main].
Traceback (most recent call last):
  File "/srv/launchpad.net/codelines/current/scripts/ftpmaster-tools/sync-source.py", line 940, in <module>
    main()
  File "/srv/launchpad.net/codelines/current/scripts/ftpmaster-tools/sync-source.py", line 936, in main
    do_diff(Sources, Suite, origin, arguments, current_binaries)
  File "/srv/launchpad.net/codelines/current/scripts/ftpmaster-tools/sync-source.py", line 725, in do_diff
    Options.requestor, origin, Suite, current_binaries)
  File "/srv/launchpad.net/codelines/current/scripts/ftpmaster-tools/sync-source.py", line 673, in add_source
    current_sources, current_binaries)
  File "/srv/launchpad.net/codelines/current/scripts/ftpmaster-tools/sync-source.py", line 495, in import_dsc
    origin)
  File "/srv/launchpad.net/codelines/current/scripts/ftpmaster-tools/sync-source.py", line 175, in generate_changes
    changes += changelog
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 921: ordinal not in range(128)

The first time I tried this, my locale was C. I tried setting it to en_GB.UTF-8 (which exists on cocoplum), but that made no difference.

The relevant line from the changelog is this:

  * French translation updated by David Prévot (closes: #593990)

I've checked that this is correctly encoded in UTF-8 as 0xC3 0xA9:

lp_archive@cocoplum:~/syncs$ tar xzOf dctrl-tools_2.15.tar.gz dctrl-tools-2.15/debian/changelog | head -n35 | grep 'French translation' | hd
00000000 20 20 2a 20 46 72 65 6e 63 68 20 74 72 61 6e 73 | * French trans|
00000010 6c 61 74 69 6f 6e 20 75 70 64 61 74 65 64 20 62 |lation updated b|
00000020 79 20 44 61 76 69 64 20 50 72 c3 a9 76 6f 74 20 |y David Pr..vot |
00000030 28 63 6c 6f 73 65 73 3a 20 23 35 39 33 39 39 30 |(closes: #593990|
00000040 29 0a |).|
00000042

I've marked this as a regression in the bug summary. While I'm not absolutely certain about this, Debian changelogs have been specified as UTF-8 for several years now and UTF-8 is often used in translation credits in changelogs, so I find it implausible that we wouldn't have run across this before now. However, none of the recent changes to sync-source.py seem to be likely candidates. Perhaps this is something to do with the recent upgrade of cocoplum to lucid?