Thread:Project:Support desk/Mediawiki 1.25.1 error: Class 'MWLoggerFactory' not found

I'm upgrading a site to 1.25.1 and am getting this error "PHP Fatal error: Class 'MWLoggerFactory' not found in /var/www/html/extensions/Math/MathRenderer.php on line 175" Any idea how to fix this? I have read about this on several areas & it seems it is a known issue with this upgrade. please poit me in the right direction.