autobuild[sn-devel-144]: intermittent test failure detected

[autobuild]

The autobuild test system (on sn-devel-144) has detected an intermittent failing test in 
the current master tree.

The autobuild log of the failure is available here:

   https://git.samba.org/autobuild.flakey.sn-devel-144/2019-03-29-0103/flakey.log

The failure seems to be in the "samba-ad-dc-ntvfs" suite, whose build logs are available here:

   https://git.samba.org/autobuild.flakey.sn-devel-144/2019-03-29-0103/samba-ad-dc-ntvfs.stderr
   https://git.samba.org/autobuild.flakey.sn-devel-144/2019-03-29-0103/samba-ad-dc-ntvfs.stdout
  
The top commit at the time of the failure was:

commit c68d9c9ef367c1e85619ac2d027a0a425164ca8a
Author: David Disseldorp <ddiss at samba.org>
Date:   Mon Mar 25 18:06:15 2019 +0100

    vfs_snapper: drop unneeded fstat handler
    
    fstat is handle based, and unlike vfs_shadow_copy2, we don't need to
    make any changes to the returned sbuf, so remove the existing handler
    which does nothing.
    
    Bug: https://bugzilla.samba.org/show_bug.cgi?id=13858
    
    Signed-off-by: David Disseldorp <ddiss at samba.org>
    Reviewed-by: Jeremy Allison <jra at samba.org>
    
    Autobuild-User(master): Jeremy Allison <jra at samba.org>
    Autobuild-Date(master): Wed Mar 27 18:21:38 UTC 2019 on sn-devel-144

and the last 50 lines of the stdout log were:

[215(856)/252 at 24m50s] samba4.smb.signing on with -k yes --signing=on(ad_dc_ntvfs)
[216(857)/252 at 24m51s] samba4.smb.signing on with -k yes --signing=required(ad_dc_ntvfs)
[217(858)/252 at 24m52s] samba4.smb.signing on with -k yes --option=gensec:fake_gssapi_krb5=yes --option=gensec:gssapi_krb5=no --signing=on(ad_dc_ntvfs)
[218(859)/252 at 24m53s] samba4.smb.signing on with -k yes --option=gensec:fake_gssapi_krb5=yes --option=gensec:gssapi_krb5=no --signing=required(ad_dc_ntvfs)
[219(860)/252 at 24m54s] samba4.smb.signing --signing=yes anon(ad_dc_ntvfs)
[220(861)/252 at 24m55s] samba4.smb.signing --signing=required anon(ad_dc_ntvfs)
[221(862)/252 at 24m55s] samba.tests.complex_expressions(ad_dc_ntvfs)
[222(884)/252 at 25m5s] samba.tests.samba_tool.gpo(ad_dc_ntvfs:local)
[223(896)/252 at 26m0s] samba.tests.dcerpc.registry(ad_dc_ntvfs:local)
[224(899)/252 at 26m0s] samba.tests.dcerpc.dnsserver(ad_dc_ntvfs)
[225(916)/252 at 26m22s] samba.tests.auth_log(ad_dc_ntvfs:local)
[226(963)/252 at 27m3s] samba.tests.auth_log_pass_change(ad_dc_ntvfs)
[227(971)/252 at 27m14s] samba.tests.auth_log_ncalrpc(ad_dc_ntvfs:local)
[228(973)/252 at 27m15s] samba.tests.auth_log_samlogon(ad_dc_ntvfs:local)
[229(974)/252 at 27m16s] samba.tests.auth_log_netlogon(ad_dc_ntvfs:local)
[230(975)/252 at 27m18s] samba.tests.auth_log_netlogon_bad_creds(ad_dc_ntvfs:local)
[231(979)/252 at 27m21s] samba.tests.password_hash_fl2008(ad_dc_ntvfs:local)
[232(983)/252 at 27m24s] samba.tests.krb5_credentials(ad_dc_ntvfs)
[233(986)/252 at 27m27s] samba.tests.py_credentials(ad_dc_ntvfs)
[234(994)/252 at 27m35s] samba.tests.emulate.traffic(ad_dc_ntvfs)
[235(996)/252 at 27m35s] samba.tests.emulate.traffic_packet(ad_dc_ntvfs)
[236(1085)/252 at 29m41s] samba.tests.blackbox.traffic_replay(ad_dc_ntvfs)
[237(1090)/252 at 30m19s] samba.tests.blackbox.traffic_learner(ad_dc_ntvfs)
[238(1092)/252 at 30m20s] samba.tests.blackbox.traffic_summary(ad_dc_ntvfs)
[239(1092)/252 at 30m21s] samba.tests.blackbox.smbcontrol(ad_dc_ntvfs:local)
[240(1094)/252 at 30m24s] samba4.urgent_replication.python(ad_dc_ntvfs)(ad_dc_ntvfs:local)
[241(1102)/252 at 30m30s] samba4.ldap.match_rules.python(ad_dc_ntvfs)
[242(1136)/252 at 31m4s] samba4.ldap.notification.python(ad_dc_ntvfs)(ad_dc_ntvfs)
UNEXPECTED(failure): samba4.ldap.notification.python(ad_dc_ntvfs).__main__.LDAPNotificationTest.test_simple_search(ad_dc_ntvfs)
REASON: Exception: Exception: Traceback (most recent call last):
  File "/memdisk/autobuild/fl/b1798175/samba-ad-dc-ntvfs/source4/dsdb/tests/python/notification.py", line 151, in test_simple_search
    self.assertIsNotNone(msg3)
AssertionError: unexpectedly None

FAILED (1 failures, 0 errors and 0 unexpected successes in 0 testsuites)

A summary with detailed information can be found in:
  ./bin/ab/summary
TOP 10 slowest tests
samba.tests.emulate.traffic_packet(ad_dc_ntvfs) -> 126
samba4.raw.notify(ad_dc_ntvfs) -> 114
samba4.nbt.winsreplication(ad_dc_ntvfs) -> 73
samba4.ntvfs.cifs.krb5.base.deny2(ad_dc_ntvfs) -> 60
samba4.base.deny2(ad_dc_ntvfs) -> 59
samba.tests.samba_tool.gpo(ad_dc_ntvfs:local) -> 55
samba4.ntvfs.cifs.krb5.base.deny1(ad_dc_ntvfs) -> 54
samba4.base.deny1(ad_dc_ntvfs) -> 53
samba4.raw.oplock(ad_dc_ntvfs) -> 51
samba4.ntvfs.cifs.krb5.base.delete(ad_dc_ntvfs) -> 46
ERROR: test failed with exit code 1