Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; Event_Notification has a deprecated constructor in /var/www/web141/html/piwik/libs/Event/Notification.php on line 66
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Error: Unable to start session. Please check that the web server has enough permission to write to these files/directories:
For example, on a Linux server if your Apache httpd user is www-data, you can try to execute:
chown -R www-data:www-data /var/www/web141/html/piwik/tmp/sessions/
chmod -R 0755 /var/www/web141/html/piwik/tmp/sessions/

Debug: the original error was 
Session must be started before any output has been sent to the browser; output started in /var/www/web141/html/piwik/libs/Event/Notification.php/66

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