Hi,

I almost got the test running with some additional fixes
(available at lp:~vila/loggerhead/export-tarball) only to run
into a bug in bzr itself (I think you should be able to fix that
one ;).

Note that your code requires bzr >= 2.4 (launchpad only runs
2.3.3 so far) so we'll need some support from the lp guys to
deploy a more recent version there.

Summary of my fixes:

- you need to create a branch (with some content even) before
  being able to call

         app = self.setUpLoggerhead()

  So I've added a setUp method for your class to do that.  You
  probably want to add *more* tests to check that you get a valid
  tarball with the expected content (which an empty branch
  doesn't allow ;).

- you're calling get_export_generator without dest nor root and
  the code in bzrlib defaults to dest to set root. This raises an
  interesing point: which root should be used here (i.e. what do
  we want to prefix all the paths in the archive
  with). <project>-<branch nick>-<revno> may be nice (but ask
  others for feedback too).

- you used '.tar.gz' for the format but bzr expects either 'tgz'
  OR a dest file name to deduce the format from the file
  suffix. I just used 'tgz' there.

With these fixes in place we get:

======================================================================
ERROR: bzrlib.plugins.loggerhead.loggerhead.tests.test_controllers.TestDownloadTarballUI.test_download_tarball
----------------------------------------------------------------------
_StringException: Text attachment: log
------------
0.622  creating repository in file:///tmp/testbzr-KY_qfE.tmp/bzrlib.plugins.loggerhead.loggerhead.tests.test_controllers.TestDownloadTarballUI.test_download_tarball/work/.bzr/.
0.624  creating branch <bzrlib.branch.BzrBranchFormat7 object at 0x22ae990> in file:///tmp/testbzr-KY_qfE.tmp/bzrlib.plugins.loggerhead.loggerhead.tests.test_controllers.TestDownloadTarballUI.test_download_tarball/work/
0.631  trying to create missing lock '/tmp/testbzr-KY_qfE.tmp/bzrlib.plugins.loggerhead.loggerhead.tests.test_controllers.TestDownloadTarballUI.test_download_tarball/work/.bzr/checkout/dirstate'
0.631  opening working tree '/tmp/testbzr-KY_qfE.tmp/bzrlib.plugins.loggerhead.loggerhead.tests.test_controllers.TestDownloadTarballUI.test_download_tarball/work'
0.642  export version <InventoryRevisionTree instance at 29ece90, rev_id='null:'>
0.649  opening working tree '/tmp/testbzr-KY_qfE.tmp'
------------
Text attachment: traceback
------------
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/testtools/runtest.py", line 169, in _run_user
    return fn(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/testtools/testcase.py", line 499, in _run_test_method
    return self._get_test_method()()
  File "/home/vila/.bazaar/plugins/loggerhead/loggerhead/tests/test_controllers.py", line 140, in test_download_tarball
    res = app.get('/tarball')
  File "/usr/lib/pymodules/python2.7/paste/fixture.py", line 208, in get
    return self.do_request(req, status=status)
  File "/usr/lib/pymodules/python2.7/paste/fixture.py", line 389, in do_request
    **req.environ)
  File "/usr/lib/pymodules/python2.7/paste/wsgilib.py", line 346, in raw_interactive
    for s in app_iter:
  File "/usr/lib/pymodules/python2.7/paste/lint.py", line 265, in next
    v = self.iterator.next()
  File "/home/vila/.bazaar/plugins/loggerhead/loggerhead/exporter.py", line 43, in export_archive
    for _ in get_export_generator(tree=tree, root=root, fileobj=fileobj, format=format):
  File "/home/vila/src/bzr/trunk/bzrlib/export/__init__.py", line 129, in get_export_generator
    force_mtime=force_mtime, fileobj=fileobj):
  File "/home/vila/src/bzr/trunk/bzrlib/export/tar_exporter.py", line 155, in tgz_exporter_generator
    zipstream = gzip.GzipFile(basename, 'w', fileobj=stream,
UnboundLocalError: local variable 'basename' referenced before assignment
------------

----------------------------------------------------------------------
Ran 44 tests in 1.933s

FAILED (errors=1)