A weird apt bug

I recently came into possession of computer running Ubuntu 10.04 (yes, in 2021). Perhaps the complete setup steps will be another post. But I mostly want to document this error that I ran into after attempting to `apt-get upgrade`, since it has only been mentioned one other place on the internet.

The error would come up whenever attempting to use `dpkg`. Most annoyingly this was through most `apt-get` commands. But the most direct way of reproducing was running `dpkg` in a terminal:

```sh
root:~# dpkg
dpkg: configuration error: /etc/dpkg/dpkg.cfg.d/01_no_documentation:1: unknown option 'path-exclude'
```

Now, `path-exclude` is a perfectly valid option for a dpkg config file. The issue here is with the dpkg binary. I fixed the issue by replacing dpkg with a copy from another computer of the same model.

I'm still not sure why this happened, or if there is a more elegant way of fixing it.