Add a check to the constructor of the new redis store to check if predis/predis is available, and throw a critical configuration error if not.
Add a check to the constructor of the new redis store to check if predis/predis is available, and throw a critical configuration error if not.

dnmvisser/simplesamlphp,dnmvisser/simplesamlphp,dnmvisser/simplesamlphp,simplesamlphp/simplesamlphp,ghalse/simplesamlphp,simplesamlphp/simplesamlphp,simplesamlphp/simplesamlphp,ghalse/simplesamlphp,ghalse/simplesamlphp,dnmvisser/simplesamlphp,ghalse/simplesamlphp,simplesamlphp/simplesamlphp