"E: Unable to locate package nzbdrone" during install

[mostlycarbonite]

Sonarr version (exact version): n/a
Mono version (if Sonarr is not running on Windows): 4.2.3
OS: Mint
Description of issue:

$ sudo apt-get update
... normal output here

$ sudo apt-get install nzbdrone
Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package nzbdrone

I’m reinstalling after what appears to be a failed update. Now I can’t install it at all. What’s up?

[mostlycarbonite]

nvm, I removed it with apt-get because apt-get was telling me it was already installed. I guess that also removes the source from the sources list.