I saw this at least 10 times in the last weeks.
[1425/1517 in 1h12m22s] samba4.nss.test using winbind(s3dc)
UNEXPECTED(failure): samba4.nss.test using winbind(s3dc).run nsstest(s3dc)
REASON: _StringException: _StringException: ERROR setpwent: NSS_STATUS=-1 1 (nss_errno=0)
ERROR getpwent: NSS_STATUS=-1 1 (nss_errno=0)
ERROR endpwent: NSS_STATUS=-1 1 (nss_errno=0)
ERROR setgrent: NSS_STATUS=-1 1 (nss_errno=0)
ERROR getgrent: NSS_STATUS=-1 1 (nss_errno=0)
ERROR endgrent: NSS_STATUS=-1 1 (nss_errno=0)
ERROR Non existent user gave error -1
ERROR Non existent uid gave error -1
ERROR Non existent group gave error -1
ERROR Non existent gid gave error -1
total_errors=10
FAILED (1 failures, 0 errors and 0 unexpected successes in 0 testsuites)
metze
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Fri Jun 15 20:24:11 CEST 2012 on sn-devel-104
^samba3.raw.acls.inheritance\(plugin_s4_dc\) # Seems to flap - succeeds on sn-devel, fails on Fedora 16
^samba3.raw.samba3checkfsp.samba3checkfsp\(plugin_s4_dc\) # Seems to flap - succeeds on sn-devel, fails on Fedora 16
^samba3.raw.samba3closeerr.samba3closeerr\(plugin_s4_dc\) # Seems to flap - succeeds on sn-devel, fails on Fedora 16
+^samba4.nss.test.*using.*winbind\(s3dc\).run.*nsstest # fails sometimes on sn-devel