I could neither run the upstream Docker image nor could I build the Dockerfile.
Bug 1
-----
Cannot run the upstream image:
```
docker pull jess/spotify
docker run -it --rm jess/spotify
spotify: error while loading shared libraries: libSM.so.6: cannot open shared object file: No such file or directory
```
Solution to bug 1
-----------------
Install `libsm6`
Bug 2
-----
Cannot build the Dockerfile:
```
cd dockerfiles/spotify
docker build . --pull
[...]
Warning: apt-key is deprecated. Manage keyring files in trusted.gpg.d instead (see apt-key(8)).
Executing: /tmp/apt-key-gpghome.k3eQma7IzG/gpg.1.sh --keyserver keyserver.ubuntu.com --recv-keys 4773BD5E130D1D45
gpg: key 4773BD5E130D1D45: public key "Spotify Public Repository Signing Key <tux@spotify.com>" imported
gpg: Total number processed: 1
gpg: imported: 1
Hit:1 http://deb.debian.org/debian sid InRelease
Get:2 http://repository.spotify.com stable InRelease [3316 B]
Err:2 http://repository.spotify.com stable InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY D1742AD60D811D58
Reading package lists...
W: GPG error: http://repository.spotify.com stable InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY D1742AD60D811D58
E: The repository 'http://repository.spotify.com stable InRelease' is not signed.
The command '/bin/sh -c apt-get update && apt-get install -y dirmngr gnupg --no-install-recommends apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 4773BD5E130D1D45 echo "deb http://repository.spotify.com stable non-free" >> /etc/apt/sources.list.d/spotify.list && apt-get update && apt-get install -y sa-utils libgl1-mesa-dri libgl1-mesa-glx libpulse0 spotify-client utils --no-install-recommends && rm -rf /var/lib/apt/lists/*' returned a non-zero code: 100
```
Solution to bug 2
-----------------
Replaced instructions to retrieve the key with the official instructions from https://www.spotify.com/us/download/linux/
python2 has reached end of life, so replacing it with python3.
In addition, pip (python3 version) comes along with the python3 install
on alpine, so no need to install that explicitly.
