magento 2 Please re-run Magento compile command
Depending on your configuration it may also be unecessary. If you are in default
or dev
mode you do not need it.
You just need it on production
mode
From command line and from your Magento root path:
php bin/magento setup:di:compile
P.S: After installing your module make sure you ran:
php bin/magento setup:upgrade