Calls to db.newid in separate processes can race, resulting in duplicate
ids and failed database insertion.

Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.6/roundup/mailgw.py", line 1388, in
handle_Message
    return self.handle_message(message)
  File "/usr/lib/pymodules/python2.6/roundup/mailgw.py", line 1444, in
handle_message
    return self._handle_message(message)
  File "/usr/lib/pymodules/python2.6/roundup/mailgw.py", line 1522, in
_handle_message
    parsed_message.create_msg()
  File "/usr/lib/pymodules/python2.6/roundup/mailgw.py", line 1098, in
create_msg
    messageid=messageid, inreplyto=inreplyto, **msg_props)
  File "/usr/lib/pymodules/python2.6/roundup/backends/rdbms_common.py",
line 2945, in create
    newid = self.create_inner(**propvalues)
  File "/usr/lib/pymodules/python2.6/roundup/backends/rdbms_common.py",
line 1630, in create_inner
    self.db.addnode(self.classname, newid, propvalues)
  File "/usr/lib/pymodules/python2.6/roundup/backends/rdbms_common.py",
line 948, in addnode
    self.sql(sql, vals)
  File "/usr/lib/pymodules/python2.6/roundup/backends/rdbms_common.py",
line 219, in sql
    cursor.execute(sql, args)
IntegrityError: PRIMARY KEY must be unique

Recommend atomically incrementing the id first, and then reading it.