I'm guessing it is just a bug. I know it was recently changed in the 2.4 series to call __enter__ for you, which it did not do in the past. I'm guessing the setup_ui=False path was just not tested. John =:-> <div class="gmail_quote">On Mon, Jun 20, 2011 at 12:03 PM, Zygmunt Krynicki <<a href="mailto:zygmunt.krynicki@canonical.com">zygmunt.krynicki@canonical.com</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"> Hi. On 2.4.0~beta4-1~bazaar1~natty1 Calling bzrlib.initialize(setu_ui=False) with the intent to use SilentUIFactory() is broken. The code goes to initialize with BzrLibraryState(ui=None) and immediately calls _start(). This in turn calls ui.__enter__() which fails with the following backtrace: (parts not relevant to bzr were removed) File "/home/zyga/Linaro/lava-ci/lava_ci/component.py", line 347, in __init__ self._bzr = initialize(setup_ui=False) File "/usr/lib/python2.7/dist-packages/bzrlib/__init__.py", line 185, in initialize state._start() File "/usr/lib/python2.7/dist-packages/bzrlib/library_state.py", line 93, in _start self._ui.__enter__() AttributeError: 'NoneType' object has no attribute '__enter__' Best regards ZK </blockquote></div>