dbgen sometimes crashes with "something bad happened while transforming data files. ([Errno 13] Permission denied: './tpch-dbgen/<tablename>.tbl')"

[slavong]

During prepare phase, there is an issue with dbgen crashing occasionally, because the privileges of the generated files get mixed up.
Only solution at the moment is to delete the files and start the prepare phase again.
More details will be added if this happens locally. In my case it happenned during travis CI build and there was no way how to list the folder after crash.