Code review comment for lp:~jelmer/bzr/more-lazy-hooks

One test failure when run on babune:
http://babune.ladeuil.net:24842/view/debug/job/selftest-subset-all/108/aggregatedTestReport/

<<< bzrlib.tests.test_branch.TestHooks.test_constructor
Stack Trace

_StringException: Text attachment: log
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1426.373 opening working tree '/private/tmp/testbzr-EefziM.tmp'
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Text attachment: traceback
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Traceback (most recent call last):
  File "/home/vila/lib/python/testtools/runtest.py", line 144, in _run_user
  File "/home/vila/lib/python/testtools/testcase.py", line 487, in _run_test_method
  File "/Users/babune/babune/slaves/macadam.local/workspace/selftest-subset-macadam/bzrlib/tests/test_branch.py", line 574, in test_constructor
    hooks = _mod_branch.BranchHooks("bzrlib.tests.test_branch", "branch.hooks")
TypeError: __init__() takes exactly 1 argument (3 given)
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Since the changes are pretty mechanical, it's probably shallow, so tweak.