On...
$ gpg2 --card-status
gpg: WARNING: The GNOME keyring manager hijacked the GnuPG agent.
gpg: WARNING: GnuPG will not work properly - please configure that tool to not interfere with the GnuPG system!
The gpg-agent is hijacked by gnome keyring :
$ echo $GPG_AGENT_INFO
/run/user/1000/keyring/gpg:0:1
Soluce: start a gpg agent and change the GPG_AGENT_INFO variable:
$ gpg-agent --daemon
GPG_AGENT_INFO=/tmp/gpg-Kd7kIC/S.gpg-agent:4415:1; export GPG_AGENT_INFO; #copy this line below
$ GPG_AGENT_INFO=/tmp/gpg-Kd7kIC/S.gpg-agent:4415:1; export GPG_AGENT_INFO;