def downgrade():
    op.add_column('feedback', sa.Column('author', sa.VARCHAR(length=20), nullable=True))
    op.drop_constraint(None, 'feedback', type_='foreignkey')
def downgrade():
    op.add_column('feedback', sa.Column('author', sa.VARCHAR(length=20), nullable=True))
    op.drop_constraint(None, 'feedback', type_='foreignkey')