renameColumn throws an error when renaming enum column type on MySQL

[andybee]

Environment

Knex version: 2.4.2
Database + version: MySQL 5.6.51
OS: Oracle Linux

Bug

When attempting to rename an enum column type in a migration, an error is thrown:

migration failed with error: object is not iterable (cannot read property Symbol(Symbol.iterator))
TypeError: object is not iterable (cannot read property Symbol(Symbol.iterator))
    at ./node_modules/knex/lib/dialects/mysql/schema/mysql-tablecompiler.js:86:48
    at async Runner.ensureConnection (./node_modules/knex/lib/execution/runner.js:300:14)
    at async Runner.run (./node_modules/knex/lib/execution/runner.js:30:19)
    at async Migrator._runBatch (./node_modules/knex/lib/migrations/migrate/Migrator.js:381:19)

Example migrations that replicate the error:

exports.up = (knex) => knex.schema
  .createTable('example', (table) => {
    table.enu('status', ['a', 'b', 'c']).default('a').notNullable();
  });

exports.down = () => {};

exports.up = (knex) => knex.schema
  .alterTable('example', (table) => {
    table.renameColumn('status', 'alternative');
  });

exports.down = () => {};