can't branch a repo with ERROR httplib.BadStatusLine: ''

kelvin@XPS-13:~/Project/canonical$ bzr branch lp:ubuntu/software-center
bzr: ERROR: httplib.BadStatusLine: ''

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/bzrlib/commands.py", line 930, in exception_to_return_code
    return the_callable(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/commands.py", line 1121, in run_bzr
    ret = run(*run_argv)
  File "/usr/lib/python2.7/dist-packages/bzrlib/commands.py", line 673, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/usr/lib/python2.7/dist-packages/bzrlib/commands.py", line 697, in run
    return self._operation.run_simple(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/cleanup.py", line 136, in run_simple
    self.cleanups, self.func, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/cleanup.py", line 166, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/bzrlib/builtins.py", line 1452, in run
    from_location)
  File "/usr/lib/python2.7/dist-packages/bzrlib/controldir.py", line 781, in open_tree_or_branch
    return controldir._get_tree_branch()
  File "/usr/lib/python2.7/dist-packages/bzrlib/remote.py", line 761, in _get_tree_branch
    return None, self.open_branch(name=name)
  File "/usr/lib/python2.7/dist-packages/bzrlib/remote.py", line 795, in open_branch
    ignore_fallbacks=ignore_fallbacks)
  File "/usr/lib/python2.7/dist-packages/bzrlib/remote.py", line 777, in _open_branch
    possible_transports=possible_transports)
  File "/usr/lib/python2.7/dist-packages/bzrlib/remote.py", line 3372, in __init__
    hook(self)
  File "/usr/lib/python2.7/dist-packages/bzrlib/plugins/launchpad/__init__.py", line 131, in _check_is_up_to_date
    lp_api_lite.report_freshness(the_branch, verbosity, latest_pub)
  File "/usr/lib/python2.7/dist-packages/bzrlib/plugins/launchpad/lp_api_lite.py", line 285, in report_freshness
    latest_ver, branch_ver = _get_newest_versions(the_branch, latest_pub)
  File "/usr/lib/python2.7/dist-packages/bzrlib/plugins/launchpad/lp_api_lite.py", line 219, in _get_newest_versions
    latest_ver = latest_pub.get_latest_version()
  File "/usr/lib/python2.7/dist-packages/bzrlib/plugins/launchpad/lp_api_lite.py", line 147, in get_latest_version
    json_info = self._get_lp_info()
  File "/usr/lib/python2.7/dist-packages/bzrlib/plugins/launchpad/lp_api_lite.py", line 125, in _get_lp_info
    response = urllib2.urlopen(req)
  File "/usr/lib/python2.7/urllib2.py", line 154, in urlopen
    return opener.open(url, data, timeout)
  File "/usr/lib/python2.7/urllib2.py", line 431, in open
    response = self._open(req, data)
  File "/usr/lib/python2.7/urllib2.py", line 449, in _open
    '_open', req)
  File "/usr/lib/python2.7/urllib2.py", line 409, in _call_chain
    result = func(*args)
  File "/usr/lib/python2.7/urllib2.py", line 1240, in https_open
    context=self._context)
  File "/usr/lib/python2.7/urllib2.py", line 1200, in do_open
    r = h.getresponse(buffering=True)
  File "/usr/lib/python2.7/httplib.py", line 1127, in getresponse
    response.begin()
  File "/usr/lib/python2.7/httplib.py", line 453, in begin
    version, status, reason = self._read_status()
  File "/usr/lib/python2.7/httplib.py", line 417, in _read_status
    raise BadStatusLine(line)
BadStatusLine: ''

bzr 2.7.0dev1 on python 2.7.9 (Linux-3.19.0-28-generic-x86_64-with-
    Ubuntu-15.04-vivid)
arguments: ['/usr/bin/bzr', 'branch', 'lp:ubuntu/software-center']
plugins: bash_completion[2.7.0dev1], builddeb[2.8.6],
    changelog_merge[2.7.0dev1], colo[0.4.0], grep[2.7.0dev1],
    launchpad[2.7.0dev1], netrc_credential_store[2.7.0dev1],
    news_merge[2.7.0dev1], pipeline[1.5.0], po_merge[2.7.0dev1],
    weave_fmt[2.7.0dev1]
encoding: 'utf-8', fsenc: 'UTF-8', lang: 'en_US.UTF-8'