I'm occasionally seeing this error in my Buildbot logs.

<pre>
fossil pull && fossil update
 in dir (timeout 1200 secs)
 watching logfiles {}
 argv: fossil pull && fossil update
 environment:

  LANG=en_GB.UTF-8
  LOGNAME=buildbot
  LS_COLORS=&lt;snip very long string&gt;

  PATH=&lt;snip very long string&gt;


  start
  SUDO_GID=1000
  SUDO_UID=1000
  SUDO_USER=fatman
  TERM=screen-bce
  USER=buildbot
  USERNAME=buildbot
 closing stdin
 using PTY: False
Server:
                Bytes      Cards  Artifacts     Deltas

Sent:             146          2          0          0
waiting for server...
processed: 100%         fossil:
Error: Database error: database is locked
DELETE FROM unclustered WHERE rid IN (SELECT rid FROM private)
program finished with exit code 1
elapsedTime=0.172838
</pre>

The build runs every 8 hours. Usually it's fine, but sometimes this happens and causes the build to fail.