reportbug: crashes on BTS query returning "HTTPError 500 Internal Server Error"

[Impact]

 * This issue affects the people who want to interact with Debian BTS on Ubuntu.

[Test Case]

$ reportbug -B debian
Please enter the name of the package in which you have found a problem, or type 'other' to report a more general problem.
> wnpp
Are you sure you want to file a WNPP report? [y|N|q|?]? y
*** Welcome to reportbug. Use ? for help at prompts. ***
Note: bug reports are publicly archived (including the email address of the submitter).
Detected character set: UTF-8
Please change your locale if this is incorrect.

Using '"Shih-Yuan Lee (FourDollars)" <email address hidden>' as your from address.
Will send report to Debian (per request).
What sort of request is this? (If none of these things mean anything to you, or you are trying to report a bug in an existing package, please press Enter to exit reportbug.)

1 ITP This is an `Intent To Package'. Please submit a package description along with copyright and URL in such a report.
2 O The package has been `Orphaned'. It needs a new maintainer as soon as possible.
3 RFA This is a `Request for Adoption'. Due to lack of time, resources, interest or something similar, the current maintainer is asking for someone else to maintain this package. They will maintain it in the meantime, but perhaps
       not in the best possible way. In short: the package needs a new maintainer.
4 RFH This is a `Request For Help'. The current maintainer wants to continue to maintain this package, but they needs some help to do this, because their time is limited or the package is quite big and needs several maintainers.
5 RFP This is a `Request For Package'. You have found an interesting piece of software and would like someone else to maintain it for Debian. Please submit a package description along with copyright and URL in such a report.

Choose the request type: 1
Please enter the proposed package name: kore
Checking status database...
Please briefly describe this package; this should be an appropriate short description for the eventual package: Fast SPDY capable web server for web development in C
Your report will be carbon-copied to debian-devel, per Debian policy.
Querying Debian BTS for reports on wnpp (source)...
Traceback (most recent call last):
  File "/usr/bin/reportbug", line 2217, in <module>
    main()
  File "/usr/bin/reportbug", line 1079, in main
    return iface.user_interface()
  File "/usr/bin/reportbug", line 1709, in user_interface
    latest_first=self.options.latest_first)
  File "/usr/lib/pymodules/python2.7/reportbug/ui/text_ui.py", line 517, in handle_bts_query
    source=source, http_proxy=http_proxy, archived=archived)
  File "/usr/lib/pymodules/python2.7/reportbug/debbugs.py", line 1276, in get_reports
    stats = debianbts.get_status(bugs)
  File "/usr/lib/pymodules/python2.7/debianbts.py", line 161, in get_status
    reply = server.get_status(*nr)
  File "/usr/lib/pymodules/python2.7/SOAPpy/Client.py", line 470, in __call__
    return self.__r_call(*args, **kw)
  File "/usr/lib/pymodules/python2.7/SOAPpy/Client.py", line 492, in __r_call
    self.__hd, self.__ma)
  File "/usr/lib/pymodules/python2.7/SOAPpy/Client.py", line 363, in __call
    config = self.config)
  File "/usr/lib/pymodules/python2.7/SOAPpy/Client.py", line 252, in call
    raise HTTPError(code, msg)
SOAPpy.Errors.HTTPError: <HTTPError 500 Internal Server Error>

[Regression Potential]

 * None

[Other Info]

 * This issue only happens on trusty and vivid. There is no problem for wily.
 * The patch is taken from the upstream directly. https://github.com/venthur/python-debianbts/pull/5/files