To accelerate website speed, we can deploy all static files in advance so that when send a request to website in Magento 2, it only needs to give back the link to this file. The command to run deploying is php bin/magento setup:static-content:deploy.
When an error arises in the process of deploying on a certain theme, the deployment will stop and report about it.
To skip this error and keep deploying, fix file vendor/magento/framework/Css/PreProcessor/Adapter/Less/Processor.php, commenting on line 92: throw new ContentProcessorException(new Phrase($errorMessage));
Hope the article help you find solution.