Incorrect file extension when downloading an asset

[AurelienGasser]

When using substra download, the downloaded file is zipped, but the extension is not .zip

For instance:

substra download objective d5204570-7676-48da-9ac5-ef3080e77062

creates the file metrics.py which is actually a zip file containing two files metrics.py and Dockerfile.

Examples

Objective

$ substra download objective d5204570-7676-48da-9ac5-ef3080e77062 --folder ./downloaded
$ cd downloaded
$ cat metrics.py
[some garbled binary output]
$ unzip metrics.py
Archive:  metrics.py
replace metrics.py? [y]es, [n]o, [A]ll, [N]one, [r]ename: y
  inflating: metrics.py
  inflating: Dockerfile

Algo

$ substra download algo c74acd3e-cbb5-4b82-b5f2-c8a177ef13ed --folder ./downloaded/
$ cd downloaded/
$ file algo.tar.gz
algo.tar.gz: Zip archive data, at least v2.0 to extract
$ unzip algo.tar.gz
Archive:  algo.tar.gz
  inflating: algo.py
  inflating: Dockerfile