Re-land https://codereview.chromium.org/2102003003/

third_party/buildbot_8_4p1/buildbot/master.py

 # This file is part of Buildbot.  Buildbot is free software: you can
 # redistribute it and/or modify it under the terms of the GNU General Public
 # License as published by the Free Software Foundation, version 2.
 #
 # This program is distributed in the hope that it will be useful, but WITHOUT
 # ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 # FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
 # details.
 #
 # You should have received a copy of the GNU General Public License along with
@@ skipping 290 matching lines @@
 
             try:
                 # required
                 schedulers = config['schedulers']
                 builders = config['builders']
                 slavePortnum = config['slavePortnum']
                 #slaves = config['slaves']
                 #change_source = config['change_source']
 
                 # optional
-                db_url = config.get("db_url",
-                                    "sqlite:///state.sqlite?serialize_access=1")
+                db_url = config.get("db_url", "sqlite:///state.sqlite")
                 db_poll_interval = config.get("db_poll_interval", None)
                 debugPassword = config.get('debugPassword')
                 manhole = config.get('manhole')
                 status = config.get('status', [])
                 # projectName/projectURL still supported to avoid
                 # breaking legacy configurations
                 title = config.get('title', config.get('projectName'))
                 titleURL = config.get('titleURL', config.get('projectURL'))
                 buildbotURL = config.get('buildbotURL')
                 properties = config.get('properties', {})
@@ skipping 988 matching lines @@
         self.master.addChange(change)
 
     def addBuildset(self, **kwargs):
         return self.master.addBuildset(**kwargs)
 
     def getBuilder(self, name):
         b = self.master.botmaster.builders[name]
         return BuilderControl(b, self)
 
 components.registerAdapter(Control, BuildMaster, interfaces.IControl)