Version 0.13.17 crashes on launch, can't import AddonSignals

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

## General information

### Prerequisites

* [x] Are you running the latest version?

### Description

Addon crashes on launch because it can't import AddonSignals.

### Steps to Reproduce

1. Install version 0.13.17 of this addon
2. Start Kodi

**Expected behavior:** [What you expected to happen]
The addon should be loaded.

**Actual behavior:** [What actually happened]
The addon crashes

## Context (Environment)
Linux
### Installation

* [x] 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

Kodi 18.0-RC1 Git:20181116-d99f45c
Linux Mint 19

## Debug log

https://gist.github.com/NoXPhasma/fa7c09137503255ead966ea006376306

Start by reviewing the linked debug log and the addon startup/import path for version 0.13.17. Reproduce the AddonSignals import failure with Kodi 18.0-RC1 on Linux Mint 19, then verify that the addon loads successfully after the issue is addressed.

Written by the indexing model from the issue text.