Repository: youtube-dl
Issue: youtube_dl  attribute __version__ does not exist
Labels: request

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## Checklist

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Carefully read and work through this check list in order to prevent the most common mistakes and misuse of youtube-dl:
- First of, make sure you are using the latest version of youtube-dl. Run `youtube-dl --version` and ensure your version is 2019.09.12.1. If it's not, see https://yt-dl.org/update on how to update. Issues with outdated version will be REJECTED.
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- [x] I'm reporting a feature request
- [x] I've verified that I'm running youtube-dl version **2019.09.12.1**
- [x] I've searched the bugtracker for similar feature requests including closed ones


## Description

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Hi, by [PEP 396](https://www.python.org/dev/peps/pep-0396/) `youtube_dl.__version__` should exist and report the current version of the module.
When trying this feature I get the following error:

```python
In [1]: import youtube_dl                                                                                                                                                                                                                                                                
In [2]: youtube_dl.__version__                                                                                                                                                                                                                                                           ---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)                                                                                                                                                                                                              <ipython-input-2-a225f3ac3329> in <module>()                                                                                                                                                                                                                                             ----> 1 youtube_dl.__version__                                                                                                                                                                                                                                                           
AttributeError: 'module' object has no attribute '__version__' 
```