original.js

exports.up = function(db) {
  return new Promise(function (resolve, reject) {
    db.dropTable('companies')
  }).then(
  db.createTable('companies', {
  company_id: { type: 'bigserial', primaryKey: true },
  company_name: { type: 'string', unique: true },
  domain: { type: 'string', unique: true },
  owner: 'bigint'
  })
  ).then(
  db.createTable('users', {
  user_id: { type: 'bigserial', primaryKey: true }, 
  user_name: { type: 'string', unique: true },
  mail: 'string',
  password: 'string'
  })
  );
};

right.js

function promisify(scope, fn) {
  return function() {
    var args = [].slice.call(arguments, 0)
    return new Promise(function(resolve, reject) {
      args.push(function(err, res) {
        if (err) { reject(err); return }
        resolve(res)
      })
      fn.apply(scope, args)
    })
  }
}

function migrate(action) {
  return (db, callback) => {
    action(db)
      .then(() => callback())
      .catch(callback)
  }
}

exports.up = migrate(db => {
  var dropTable = promisify(db, db.dropTable)
  var createTable = promisify(db. db.createTable)
  return dropTable('companies')
  .then(() =>
    createTable('companies', {
      company_id: { type: 'bigserial', primaryKey: true },
      company_name: { type: 'string', unique: true },
      domain: { type: 'string', unique: true },
      owner: 'bigint'
    })
  )
  .then(() =>
    createTable('users', {
      user_id: { type: 'bigserial', primaryKey: true }, 
      user_name: { type: 'string', unique: true },
      mail: 'string',
      password: 'string'
    })
  )
})