Coding error detected: must be fixed by a programmer

Coding error detected, it must be fixed by a programmer: Failed to unserialise data from file. Either failed to read, or failed to write.

Problem:
There was a file locked by cache store system.

Solutions:
1. Execute script purgecaches to reset the cache system.
    php /moodle/admin/cli/purge_caches.php
2. Remove all files and directories unde directory /moodledata/cache

Finally, please don't edit core files to solve this problem. Think, in Moodle always was a alternative solutions.

https://coderwall.com/p/py-nba/moodle-easy-solution-to-failed-to-unserialise-data-from-file-either-failed-to-read-or-failed-to-write