Downloader for the Mozilla Common Voice Datasets

[Mastercuber]

This 3 commits add support for downloading the Common Voice datasets. All today available languages are supported. If new languages will be added, the provided tests fail or a new release of the Common Voice dataset is available then the DOWNLOAD_URLS need to be modified to include/replace the new/broken URL's.

• Hopefully the commit message is OK
• flake8 gives no errors
• Docstring is added to the Downloader Class
• Used ArchivDownloader as Base so Downloader is tested
  -> Dataset availability tests (checks if HTTP HEAD Status Code is 200) are added
• Is straight with master

[Mastercuber]

I do not understand the last DeepSource error (no self). If I remove self the tests do not run at all

[ynop]

Nice, thank you.
At the moment you don't have to care about DeepSource if there is no obvious solution, I'm working on that (we have a lot of issues regarding that in the code base).

Regarding the URL availability, I think it is not good to have the tests for that in the same unit tests.
You could leave that out for now.
There is already an open issue about that (#88), but no solution so far I am really happy with.

Could you please merge the fix-commits in to the other one?

[Mastercuber]

The fix commits are squashed, the "Added Test" commit is removed, DeepSource is ignored 😄 and the Test is also removed. Should look fine now.

[ynop]

In the mean time I have worked through all the deepsource issues in the codebase.
Please rebase on the master, just to make sure you have not introduced new ones (which you haven't as far as i can see).

[Mastercuber]

Rebase onto master is done, checked with flake8 and DeepSource looks good 👍

[Mastercuber]

Travis says

1. SVML not detected
2. Failed building wheel for llvmlite
   And this for Python 3.5.
   The other Python Versions pass.

You know how to handle that problem?

[ynop]

I guess has something to do with numba/llvmlite#551, they dropped py35 support. We could try to fix on an old version (It is not fixed because it is only a subdependency of librosa -> numba). But it is not the first time that llvmlite version messes up the builds. If I remember correctly it failed last time because we fixed on a specific version.

[Mastercuber]

If audiomate will carry on support python 3.5 another library is needed if I understand it right..

Using an old version is maybe a possibility, but I sounds not right. Not supporting python 3.5 is maybe also no possibility..

[aahlenst]

The joy of transitive dependencies 🤢

I did not find any reasoning why llvmlite dropped Python 3.5 support. Following their lead is an option considering Python 3.5 reaches its EOL in September.

[Mastercuber]

5 months left. So maybe it's a possibility to just drop the support for Python 3.5...

Otherwise, I think, it would be a bit of work to fix that.. But i just suppose that..