It's not the bug in its sense, but config.inc.php missing in the phpmyadmin package. I have spent half an hour of searching the web on where that file should be located, please, include that file in the next update. Reproducible: Always
I have accidentally found it as config.sample.inc.php. The file name is bad and nobody are able to find it. Rename it to config.inc.php.sample. Thank you.
phpmyadmin is not documented for gentoo.