Windmill breaks branch-rewrite on dev systems

When starting Apache on a dev machine, we get this in the error log:

[notice] Apache/2.2.12 (Ubuntu) mod_ssl/2.2.12 OpenSSL/0.9.8g configured -- resuming normal operations
Traceback (most recent call last):
  File "/home/me/canonical/lp-branches/trunk/scripts/branch-rewrite.py", line 22, in <module>
    from canonical.launchpad.database import account
  File "/home/me/canonical/lp-branches/trunk/lib/canonical/launchpad/database/__init__.py", line 11, in <module>
    from lp.soyuz.model.sourcepackagerelease import *
  File "/home/me/canonical/lp-branches/trunk/lib/lp/soyuz/model/sourcepackagerelease.py", line 47, in <module>
    from lp.soyuz.model.build import Build
  File "/home/me/canonical/lp-branches/trunk/lib/lp/soyuz/model/build.py", line 59, in <module>
    from lp.soyuz.model.publishing import SourcePackagePublishingHistory
  File "/home/me/canonical/lp-branches/trunk/lib/lp/soyuz/model/publishing.py", line 58, in <module>
    from lp.soyuz.scripts.changeoverride import ArchiveOverriderError
  File "/home/me/canonical/lp-branches/trunk/lib/lp/soyuz/scripts/changeoverride.py", line 18, in <module>
    from lp.soyuz.scripts.ftpmasterbase import (
  File "/home/me/canonical/lp-branches/trunk/lib/lp/soyuz/scripts/ftpmasterbase.py", line 22, in <module>
    from lp.services.scripts.base import (
  File "/home/me/canonical/lp-branches/trunk/lib/lp/services/scripts/base.py", line 27, in <module>
    from lp.testing import ANONYMOUS
  File "/home/me/canonical/lp-branches/trunk/lib/lp/testing/__init__.py", line 58, in <module>
    from windmill.authoring import WindmillTestClient
  File "/home/me/canonical/lp-sourcedeps/eggs/windmill-1.3beta3_lp_r1440-py2.5.egg/windmill/__init__.py", line 17, in <module>
    import authoring, bin, browser, server, conf, tools, sys
  File "/home/me/canonical/lp-sourcedeps/eggs/windmill-1.3beta3_lp_r1440-py2.5.egg/windmill/authoring/__init__.py", line 17, in <module>
    from windmill.bin import admin_lib
  File "/home/me/canonical/lp-sourcedeps/eggs/windmill-1.3beta3_lp_r1440-py2.5.egg/windmill/bin/admin_lib.py", line 25, in <module>
    from windmill.dep import functest
  File "/home/me/canonical/lp-sourcedeps/eggs/windmill-1.3beta3_lp_r1440-py2.5.egg/windmill/dep/__init__.py", line 15, in <module>
    import _mozrunner as mozrunner
  File "/home/me/canonical/lp-sourcedeps/eggs/windmill-1.3beta3_lp_r1440-py2.5.egg/windmill/dep/_mozrunner/__init__.py", line 45, in <module>
    import global_settings
  File "/home/me/canonical/lp-sourcedeps/eggs/windmill-1.3beta3_lp_r1440-py2.5.egg/windmill/dep/_mozrunner/global_settings.py", line 42, in <module>
    def findInPath(fileName, path=os.environ['PATH']):
  File "/usr/lib/python2.5/UserDict.py", line 22, in __getitem__
    raise KeyError(key)
KeyError: 'PATH'

A workaround is to disable two windmill imports in one's local trunk/devel branch, in lib/lp/testing/__init__.py (WindmillTestClient) and lib/canonical/testing/layers.py (windmill_teardown).