Unhandled exception

* apt-local version: 0.0.2b1 (pypy latest)
* Python version: 3.8.16
* Operating System: Linux

### Description

apt-local install openssl-dev

(Note the is the wrong package name)
it should be openssl without the -dev but that should not fail badly.
Instread we get a very long backtrace and app exits ungracefully.
"subprocess.CalledProcessError: Command '['grep', '-e', ' *Depends']' returned non-zero exit status 1."

Looks like it's in need of a try/except

Reproduce the apt-local install openssl-dev command and inspect the traceback around subprocess.CalledProcessError from grep. The issue names no source file or test; done means an invalid package name exits gracefully without a long traceback or unhandled exception.

Written by the indexing model from the issue text.