def upgrade():
    op.add_column('users', sa.Column('admin', sa.Boolean(), nullable=True))
    op.execute('UPDATE users SET admin=False')
    op.alter_column('users', 'admin', nullable=False)
def upgrade():
    op.add_column('users', sa.Column('admin', sa.Boolean(), nullable=True))
    op.execute('UPDATE users SET admin=False')
    op.alter_column('users', 'admin', nullable=False)