(cherry picked from commit c6e4014136aa3d81ecd4288150b3eefca9849b0b)

See https://github.com/facebook/rocksdb/wiki/Prefix-Seek-API-Changes

* Written to the rocksdb log-file
* raise an exception back to rocksdb

On delete rocksdb waits for the background thread to finish.
However the background threads needs the GIL to execute python-code
(for example comparator)
=>
* main thread has GIL
* main thread waits for background thread
* background thread tries to get GIL
which means deadlock