I'm not sure we have write permissions on dev/stage/prod on this folder. A possible solution to that would be to place a log_cache folder in the same directory where treeherder lives. You can use the "path" function to refer to it like here https://github.com/pnispel/treeherder-service/blob/line-range-log-files/treeherder/settings/base.py#L54 substituting "media" with log_cache or something like that