Install with apt on Debian Stretch fails

[Sebastian Terhorst]

Dear community,

I tried to install Galera Cluster 5.6 on a newly installed Debian Stretch. I followed these steps:

• Create galera.list in /etc/apt/sources.list.d with content:
• deb http://releases.galeracluster.com/mysql-wsrep-5.6/debian stretch main
• deb http://releases.galeracluster.com/galera-3/debian stretch main
• Run apt-key adv --keyserver keyserver.ubuntu.com --recv BC19DDBA
• Run apt-get update

The result is:

Hit:1 http://security.debian.org/debian-security stretch/updates InRelease
Ign:2 http://deb.debian.org/debian stretch InRelease                                                                                             
Hit:3 http://deb.debian.org/debian stretch-updates InRelease                                                                                     
Hit:4 http://deb.debian.org/debian stretch Release                                 
Get:5 http://releases.galeracluster.com/mysql-wsrep-5.6/debian stretch InRelease [2,144 B]
Get:6 http://releases.galeracluster.com/galera-3/debian stretch InRelease [2,138 B]
Ign:5 http://releases.galeracluster.com/mysql-wsrep-5.6/debian stretch InRelease
Ign:6 http://releases.galeracluster.com/galera-3/debian stretch InRelease
Fetched 4,282 B in 0s (4,934 B/s)
Reading package lists... Done
W: GPG error: http://releases.galeracluster.com/mysql-wsrep-5.6/debian stretch InRelease: The following signatures were invalid: 44B7345738EBDE52594DAD80D669017EBC19DDBA
W: The repository 'http://releases.galeracluster.com/mysql-wsrep-5.6/debian stretch InRelease' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: http://releases.galeracluster.com/galera-3/debian stretch InRelease: The following signatures were invalid: 44B7345738EBDE52594DAD80D669017EBC19DDBA
W: The repository 'http://releases.galeracluster.com/galera-3/debian stretch InRelease' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.

I already cleaned all apt-get data. Any ideas?