Simple script which will update_indexes on your GAE app if there are any NoIndexErrors in your logs.

update_indexes.py

import os
import sys
from datetime import datetime

PATTERNS = [' - kind',
            '   -',
            '   properties:',
            '     direction:']

LOG_FILE_NAME = 'gae.log'
INDEX_FILE = 'index.yaml'

NUM_DAYS = 1
if len(sys.argv) > 1:
    NUM_DAYS = sys.argv[1]

def get_app_id_and_version():
    f = open('app.yaml', 'r')
    app_id = None
    ver = None
    row = f.readline()
    while row:
        if row.startswith('application:'):
            app_id = row.split(':')[1].strip()
        if row.startswith('version:'):
            ver = row.split(':')[1].strip()
        row = f.readline()

    if not app_id:
        raise Exception('Application not defined in your app.yaml file')
    if not ver:
        raise Exception('Version not defined in your app.yaml file')
    return (app_id, ver)

def build_indexes(log_file=LOG_FILE_NAME):
    f = open(log_file, 'r')

    data = f.readlines()
    data = [d.strip('\t:') for d in data]

    lines = ['indexes:', '\n']

    for a in data:
        for i, p in enumerate(PATTERNS):
            if a.startswith(p):
                if i == 0:
                    lines.append('\n')
                lines.append(a[1:]) 

    if len(lines) == 2:
        return None

    return lines

def move_original_indexes():
    os.system('mv %s %s_old' % (INDEX_FILE, INDEX_FILE))

def write_lines(lines):
    f = open(INDEX_FILE, 'w')
    f.writelines(lines)
    f.close()

def refresh_logs():
    print 'Downloading errored indexes...'
    app_id, ver = get_app_id_and_version()
    os.system('appcfg.py request_logs -A %s -V %s --oauth2 --severity=3 %s --num_days=%s' % (app_id, ver, LOG_FILE_NAME, NUM_DAYS))

def update_indexes():
    os.system('appcfg.py update_indexes .')

    built_file = 'index_update_%s.yaml' % datetime.now().strftime('%Y-%m-%d_%H-%M-%S')
    os.system('mv index.yaml %s' % built_file)
    print 'Built index moved to %s' % built_file

    os.system('mv %s_old %s' % (INDEX_FILE, INDEX_FILE))

def run():
    refresh_logs()
    index_lines = build_indexes()
    if index_lines:
        move_original_indexes()
        write_lines(index_lines)
        update_indexes()
    else:
        print 'No indexes to build'

run()