Ubuntu 18.04 add gpg key failed with gpg-agent not found error : <p>trying to migrate our base image to the stable Ubuntu 18.04, when we try to add our gpg key, getting this error:</p>

<pre><code>root@77ff14f29cab:/# apt-key add apt-key.gpg 
gpg: failed to start agent '/usr/bin/gpg-agent': No such file or directory
gpg: can't connect to the agent: No such file or directory
gpg: failed to start agent '/usr/bin/gpg-agent': No such file or directory
gpg: can't connect to the agent: No such file or directory
</code></pre>
