After upgrading from 9.0.0 to 10.0.0 cannot set uid, gid

New submission from alecm3 <None>:

New error in 10.0.0 (same code works with 9.0.0)
2010-03-05 17:39:45-0800 [-] Traceback (most recent call last):
2010-03-05 17:39:45-0800 [-]   File "/usr/local/bin/twistd", line 5, in <module>
2010-03-05 17:39:45-0800 [-]     pkg_resources.run_script('Twisted==10.0.0', 'twistd')
2010-03-05 17:39:45-0800 [-]   File "build/bdist.linux-x86_64/egg/pkg_resources.py", line 489, in run_script
2010-03-05 17:39:45-0800 [-]   File "build/bdist.linux-x86_64/egg/pkg_resources.py", line 1207, in run_script
2010-03-05 17:39:45-0800 [-]   File "/nail/encap/python-2.6.4/lib/python2.6/site-packages/Twisted-10.0.0-py2.6-linux-x86_64.egg/EGG-INFO/scripts/twistd", line 19, in <module>
2010-03-05 17:39:45-0800 [-]     run()
2010-03-05 17:39:45-0800 [-]   File "/usr/local/encap/python-2.6.4/lib/python2.6/site-packages/Twisted-10.0.0-py2.6-linux-x86_64.egg/twisted/scripts/twistd.py", line 27, in run
2010-03-05 17:39:45-0800 [-]     app.run(runApp, ServerOptions)
2010-03-05 17:39:45-0800 [-]   File "/usr/local/encap/python-2.6.4/lib/python2.6/site-packages/Twisted-10.0.0-py2.6-linux-x86_64.egg/twisted/application/app.py", line 693, in run
2010-03-05 17:39:45-0800 [-]     runApp(config)
2010-03-05 17:39:45-0800 [-]   File "/usr/local/encap/python-2.6.4/lib/python2.6/site-packages/Twisted-10.0.0-py2.6-linux-x86_64.egg/twisted/scripts/twistd.py", line 23, in runApp
2010-03-05 17:39:45-0800 [-]     _SomeApplicationRunner(config).run()
2010-03-05 17:39:45-0800 [-]   File "/usr/local/encap/python-2.6.4/lib/python2.6/site-packages/Twisted-10.0.0-py2.6-linux-x86_64.egg/twisted/application/app.py", line 423, in run
2010-03-05 17:39:45-0800 [-]     self.postApplication()
2010-03-05 17:39:45-0800 [-]   File "/usr/local/encap/python-2.6.4/lib/python2.6/site-packages/Twisted-10.0.0-py2.6-linux-x86_64.egg/twisted/scripts/_twistd_unix.py", line 205, in postApplication
2010-03-05 17:39:45-0800 [-]     self.startApplication(self.application)
2010-03-05 17:39:45-0800 [-]   File "/usr/local/encap/python-2.6.4/lib/python2.6/site-packages/Twisted-10.0.0-py2.6-linux-x86_64.egg/twisted/scripts/_twistd_unix.py", line 316, in startApplication
2010-03-05 17:39:45-0800 [-]     self.shedPrivileges(self.config['euid'], uid, gid)
2010-03-05 17:39:45-0800 [-]   File "/usr/local/encap/python-2.6.4/lib/python2.6/site-packages/Twisted-10.0.0-py2.6-linux-x86_64.egg/twisted/scripts/_twistd_unix.py", line 287, in shedPrivileges
2010-03-05 17:39:45-0800 [-]     switchUID(uid, gid, euid)
2010-03-05 17:39:45-0800 [-]   File "/usr/local/encap/python-2.6.4/lib/python2.6/site-packages/Twisted-10.0.0-py2.6-linux-x86_64.egg/twisted/python/util.py", line 677, in switchUID
2010-03-05 17:39:45-0800 [-]     initgroups(uid, gid)
2010-03-05 17:39:45-0800 [-]   File "/usr/local/encap/python-2.6.4/lib/python2.6/site-packages/Twisted-10.0.0-py2.6-linux-x86_64.egg/twisted/python/util.py", line 636, in initgroups
2010-03-05 17:39:45-0800 [-]     return _c_initgroups(pwd.getpwuid(uid)[0], primaryGid)
2010-03-05 17:39:45-0800 [-] OSError: [Errno 1] Operation not permitted

OS: Ubuntu 8.04 

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Type     : defect
Component: core
Keywords : gid
Priority : normal
Nosy     : 
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http://twistedmatrix.com/trac/ticket/4351