##エラー文
Using 'this.dialect' to identify the client is deprecated and support for it will be removed in the future. Please use configuration option 'client' instead.
##解決法
var knex = require('knex')({
dialect: 'mysql',
connection: {
host: 'localhost',
user: 'root',
password: '(パスワード)',
database: '(データベース名)',
charset: 'utf-8'
}
});
上の文の、dialectをclientに変更する。