replay.py Incorrect variable reference in exchange timestamp

[yogisec]

I came across a mis-named variable (s/path/file_path/g) on line 48 of replay.py when troubleshooting some unrelated local issues I was having. The variable path is not defined anywhere and looking at surrounding code it appears to just be a typo.

This MR also adds some really minor lint type fixes. I tried to keep those to a minimum.

I was unable to test this change, I don't actually have any exchange data. Just happened across this.