When I install Pusher package, I got an error "Class 'Pusher' not found".
Claudio's diagnosis is correct, the namespace Pusher was added in version 3; but changing the Laravel files is not a recommended solution.
A better way is to create an alias in config/app.php
. Under the 'aliases' key, add this to the array in the "Third Party Aliases" section:
'Pusher' => Pusher\Pusher::class,