While debugging for this issue Codeception/Codeception#4871, I keep getting message Could not write error to log file.
When I traced the cause, it's from here.

Apparently the c3tmp directory is always emptied by __c3_clear() when the test is executed.

This cause problem because is_writable returns true if the file exists and is writable.

http://php.net/manual/en/function.is-writable.php