sequelize/sequelize — pull request #1770 by vanetix (2014-05-14 18:32:38+00:00)
Title: Update mysql module notice

The previous logged message wasn't a clear notice of what happened, since a stack trace for errors later in the code was thrown due to the mysql module not being defined.

Example:
```
TypeError: Cannot call method 'createConnection' of undefined
at module.exports.connect (/usr/lib/node_modules/sequelize/lib/dialects/mysql/connector-manager.js:306:28)
at Object.pool.Pooling.Pool.create (/usr/lib/node_modules/sequelize/lib/dialects/mysql/connector-manager.js:131:19)
at createResource (/usr/lib/node_modules/sequelize/node_modules/generic-pool/lib/generic-pool.js:258:13)
at dispense (/usr/lib/node_modules/sequelize/node_modules/generic-pool/lib/generic-pool.js:250:9)
at Object.me.acquire (/usr/lib/node_modules/sequelize/node_modules/generic-pool/lib/generic-pool.js:316:5)
at null.fct (/usr/lib/node_modules/sequelize/lib/dialects/mysql/connector-manager.js:241:19)
at null. (/usr/lib/node_modules/sequelize/lib/emitters/custom-event-emitter.js:24:18)
at processImmediate [as _immediateCallback] (timers.js:330:15)
```

Throwing the custom error:
```
/usr/lib/node_modules/sequelize/lib/dialects/mysql/connector-manager.js:16
throw new Error('You need to install mysql package manually')
^
Error: You need to install mysql package manually
at new module.exports.ConnectorManager (/usr/lib/node_modules/sequelize/lib/dialects/mysql/connector-manager.js:16:13)
at TransactionManager.getConnectorManager (/usr/lib/node_modules/sequelize/lib/transaction-manager.js:33:36)
at TransactionManager.query (/usr/lib/node_modules/sequelize/lib/transaction-manager.js:52:15)
at module.exports.Sequelize.query (/usr/lib/node_modules/sequelize/lib/sequelize.js:330:36)
at null.fct (/usr/lib/node_modules/sequelize/lib/sequelize.js:410:10)
at null. (/usr/lib/node_modules/sequelize/lib/emitters/custom-event-emitter.js:24:18)
at processImmediate [as _immediateCallback] (timers.js:330:15)
```