Unit tests error because missing import AddonSignals

*I'm submitting a ...*
- [x] bug report
- [ ] feature request
- [ ] support request

## General information
I'm trying to run the unit tests for this project. 4 tests have errors because I'm missing the module AddonSignals

### Prerequisites

* [x] Are you running the latest version?

### Description
git clone the project
sudo pip2 install -r requirements.txt
python2 -m nose resources/test/

Four tests errored because of missing module. Has it be missed from the requirements.txt or do I have to install it another way?

## Context (Environment)

### Installation
N/A
* [ ] I installed the plugin via zip from the Releases page
* [ ] I´m using the Netflix Repo
* [ ] I´m using a different source (Please tell which)

### Operating System

* [x] Linux (x86/x64)
* [ ] OSX (x86/x64)
* [ ] Windows (x86/x64)
* [ ] Linux (ARM)
* [ ] Android

#### Additional informatin on the environment
uname -a
Linux arch 5.2.8-arch1-1-ARCH #1 SMP PREEMPT Fri Aug 9 21:36:07 UTC 2019 x86_64 GNU/Linux

## Debug log

https://pastebin.com/4e1Kqbdc

Start by checking requirements.txt and the failing tests under resources/test/, then reproduce the report with python2 -m nose resources/test/. Determine how AddonSignals is expected to be provided; the work is done when the four reported tests run without the missing-module errors.

Written by the indexing model from the issue text.