**** CubicPower OpenStack Study ****
def upgrade(active_plugins=None, options=None):
op.drop_column('ipallocations', u'expiration')
**** CubicPower OpenStack Study ****
def downgrade(active_plugins=None, options=None):
op.add_column('ipallocations', sa.Column(u'expiration', sa.DateTime(),
nullable=True))