code: def createUserObject(master, author, src=None):
      
  
      if not src:
          log.msg("No vcs information found, unable to create User Object")
          return defer.succeed(None)
  
      if src in srcs:
          usdict = dict(identifier=author, attr_type=src, attr_data=author)
      else:
          log.msg("Unrecognized source argument: %s" % src)
          return defer.succeed(None)
  
      return master.db.users.findUserByAttr(
          identifier=usdict['identifier'],
          attr_type=usdict['attr_type'],
          attr_data=usdict['attr_data'])
docs: Take a Change author and source and translate them into a User Object,
      storing the user in master.db, or returning None if the src is not
      specified.
  
      @param master: link to Buildmaster for database operations
      @type master: master.Buildmaster instance
  
      @param authors: Change author if string or Authz instance
      @type authors: string or www.authz instance
  
      @param src: source from which the User Object will be created
      @type src: string