I am currently trying to perform an upgrade of an eZ Publish 4 project to eZ Publish 5. The eZ4 project is up to date with the current Legacy master branch from github. These are the steps I performed, following the installation instructions at Github:

$ git clone https://github.com/ezsystems/ezpublish-community.git cms
$ cp -R /path/to/old/ez cms/ezpublish_legacy
$ rm -rf cms/ezpublish/legacy/vendor
$ cd cms
$ php -dmemory_limit=-1 ../bin/composer.phar install --prefer-dist

This got me the following error:

[PDOException]
SQLSTATE[HY000] [2002] No such file or directory

The same occurs when executing

php ezpublish/console ezpublish:configure --env=prod <package> <admin_siteaccess>

After some heavy debugging, I became aware that the settings from app/config/ezpublish_setup.yml are being used, and thought it would be nice if the error message would hint me to this instead of giving me just a generic error message.

You can find my proposal for this enhancement here: https://github.com/ezsystems/ezpublish-kernel/pull/709