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-144/2018-09-26-1258/flakey.log

The failure seems to be in the "samba-py3" suite, whose build logs are available here:

   https://git.samba.org/autobuild.flakey.sn-devel-144/2018-09-26-1258/samba-py3.stderr
   https://git.samba.org/autobuild.flakey.sn-devel-144/2018-09-26-1258/samba-py3.stdout
  
The top commit at the time of the failure was:

commit 36cb85be726e03c482b82f0af7eed2c81f8df35a
Author: Douglas Bagnall <douglas.bagnall at catalyst.net.nz>
Date:   Fri Sep 21 11:26:35 2018 +1200

    samba-tool domain backup: fix py2.6 incompatible format
    
    Signed-off-by: Douglas Bagnall <douglas.bagnall at catalyst.net.nz>
    Reviewed-by: Andrew Bartlett <abartlet at samba.org>
    
    Autobuild-User(master): Andrew Bartlett <abartlet at samba.org>
    Autobuild-Date(master): Wed Sep 26 10:40:49 CEST 2018 on sn-devel-144

and the last 50 lines of the stdout log were:

[49(433)/75 at 17m34s] samba4.drs.getnc_unpriv.python(vampire_dc).python3(vampire_dc)
[50(437)/75 at 17m38s] samba4.drs.link_conflicts.python(vampire_dc).python3(vampire_dc)
[51(449)/75 at 20m15s] samba4.drs.samba_tool_drs.python(promoted_dc).python3(promoted_dc:local)
[52(463)/75 at 21m50s] samba4.drs.samba_tool_drs_showrepl.python(promoted_dc).python3(promoted_dc:local)
[53(467)/75 at 22m4s] samba4.drs.replica_sync.python(promoted_dc).python3(promoted_dc:local)
[54(483)/75 at 23m22s] samba4.drs.delete_object.python(promoted_dc).python3(promoted_dc)
[55(485)/75 at 23m30s] samba4.drs.fsmo.python(promoted_dc).python3(promoted_dc)
[56(490)/75 at 23m39s] samba4.drs.repl_move.python(promoted_dc).python3(promoted_dc)
[57(511)/75 at 24m57s] samba4.drs.getnc_exop.python(promoted_dc).python3(promoted_dc)
[58(523)/75 at 25m6s] samba4.drs.getnc_unpriv.python(promoted_dc).python3(promoted_dc)
[59(527)/75 at 25m10s] samba4.drs.link_conflicts.python(promoted_dc).python3(promoted_dc)
[60(539)/75 at 28m8s] samba4.drs.repl_schema.python(vampire_dc).python3(vampire_dc)
[61(548)/75 at 28m54s] samba4.drs.repl_schema.python(promoted_dc).python3(promoted_dc)
[62(557)/75 at 29m37s] samba4.drs.getncchanges.python(vampire_dc).python3(vampire_dc)
[63(569)/75 at 31m18s] samba4.drs.getncchanges.python(promoted_dc).python3(promoted_dc)
[64(581)/75 at 33m40s] samba4.drs.repl_rodc.python(ad_dc_ntvfs).python3(ad_dc_ntvfs)
[65(589)/75 at 34m16s] samba.tests.join.python(ad_dc_ntvfs).python3(ad_dc_ntvfs)
[66(591)/75 at 36m3s] samba4.drs.cracknames.python(ad_dc_ntvfs).python3(ad_dc_ntvfs)
[67(594)/75 at 36m6s] samba.tests.kcc.python3(vampire_dc)
[68(596)/75 at 36m7s] samba.tests.samba_tool.visualize_drs.python3(vampire_dc)
[69(607)/75 at 37m26s] samba.tests.kcc.python3(promoted_dc)
UNEXPECTED(error): samba.tests.kcc.python3.samba.tests.kcc.KCCTests.test_verify(promoted_dc)
REASON: Exception: Exception: Traceback (most recent call last):
  File "bin/python/samba/tests/kcc/__init__.py", line 80, in test_verify
    attempt_live_connections=False)
  File "bin/python/samba/kcc/__init__.py", line 2659, in run
    ('connected',))
  File "bin/python/samba/kcc/__init__.py", line 2513, in plot_all_connections
    vertex_colors=vertex_colours)
  File "bin/python/samba/kcc/graph_utils.py", line 334, in verify_and_dot
    for p, e, doc in errors)))
samba.kcc.graph_utils.GraphError: The 'dsa_final CN=NTDS Settings,CN=PROMOTEDVDC,CN=Servers,CN=Default-First-Site-Name,CN=Sites,CN=Configuration,DC=samba,DC=example,DC=com' graph lacks the following properties:
connected: the graph is not connected, as the following vertices are unreachable:

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

A summary with detailed information can be found in:
  ./bin/ab/summary
TOP 10 slowest tests
samba4.drs.link_conflicts.python(promoted_dc).python3(promoted_dc) -> 179
samba4.drs.link_conflicts.python(vampire_dc).python3(vampire_dc) -> 156
samba4.drs.ridalloc_exop.python(vampire_dc).python3(vampire_dc) -> 152
samba4.drs.repl_move.python(vampire_dc).python3(vampire_dc) -> 148
samba4.drs.getncchanges.python(promoted_dc).python3(promoted_dc) -> 142
samba.tests.join.python(ad_dc_ntvfs).python3(ad_dc_ntvfs) -> 108
samba4.drs.getncchanges.python(vampire_dc).python3(vampire_dc) -> 101
samba4.drs.samba_tool_drs.python(promoted_dc).python3(promoted_dc:local) -> 96
samba4.drs.samba_tool_drs.python(vampire_dc).python3(vampire_dc:local) -> 96
samba.tests.emulate.traffic_packet.python3(ad_dc_ntvfs) -> 84
ERROR: test failed with exit code 1