I tried to install TheLeader Theme from wordpress backend but it was not possible with a generic error message.
Then I tried to install it via ftp then I could see it in theme list.
But as soon as I activate it I get the error on the subject:
Fatal error: Cannot redeclare class Woothemes_Testimonials in /var/www/html/wp-content/themes/theleader/framework/testimonials/classes/class-woothemes-testimonials.php on line 15
Everything gets broken, frontend and backend.
So I have to manually delete it with ftp.