Code review comment for lp:~andrea.corbellini/launchpad/fix-406523

Unfortunately this branch caused some test failure when I ran the full test suite.

Failure in test lib/lp/bugs/tests/../stories/bugattachments/xx-display-filesize-attachment.txt
Failed doctest test for xx-display-filesize-attachment.txt
  File "lib/lp/bugs/tests/../stories/bugattachments/xx-display-filesize-attachment.txt", line 0

----------------------------------------------------------------------
File "lib/lp/bugs/tests/../stories/bugattachments/xx-display-filesize-attachment.txt", line 48, in xx-display-filesize-attachment.txt
Failed example:
    user_browser.url
Differences (ndiff with -expected +actual):
    - 'http://bugs.launchpad.dev/firefox/+bug/1'
    + 'http://bugs.launchpad.dev/firefox/+bug/1/+addcomment'
    ? ++++++++++++
----------------------------------------------------------------------
File "lib/lp/bugs/tests/../stories/bugattachments/xx-display-filesize-attachment.txt", line 51, in xx-display-filesize-attachment.txt
Failed example:
    last_comment = find_tags_by_class(
        user_browser.contents, 'boardCommentBody')[-1]
Exception raised:
    Traceback (most recent call last):
      File "/var/launchpad/test/lib/zope/testing/doctest.py", line 1360, in __run
        compileflags, 1) in test.globs
      File "<doctest xx-display-filesize-attachment.txt[23]>", line 1, in ?
    IndexError: list index out of range
----------------------------------------------------------------------
File "lib/lp/bugs/tests/../stories/bugattachments/xx-display-filesize-attachment.txt", line 54, in xx-display-filesize-attachment.txt
Failed example:
    for attachment in last_comment('li', {'class': 'download'}):
        print extract_text(attachment)
Differences (ndiff with -expected +actual):
      description text
    - (2.6 KiB, text/plain)
    + (270 bytes,
    + text/plain)

I don't know exactly what's going on here, but the test that fails does have a connection to this code, so I doubt it's a spurious failure. Try to get it to work and let me know if you have problems.