update DBSession to comply with fields newly configured as required

gistfile1.txt

from google.appengine.ext import db
from datetime import datetime

# local override with start not being required
class DBSession(db.Model):
  start = db.DateTimeProperty()
  title = db.StringProperty()

for s in DBSession.all():
  save_it = False
  if not s.start:
    save_it = True
    s.start = datetime(2014, 1, 1)
  if not s.title:
    save_it = True
    s.title = 'space-holder-title'
  if save_it:
    s.put()