Creating or using a Wikimedia developer account will publicly expose information to other users of Wikimedia Cloud Services:
The email address you associate with your Wikimedia developer account will be publicly visible.
When connecting to virtual machines in Wikimedia Cloud VPS using SSH, your IP address will be recorded and may be visible to other users of Cloud VPS or Toolforge.
It is recommended to use a unique password that you are not using on any other website.
UNIX shell username
Your shell username will be used when logging into Toolforge and other Wikimedia VPS hosts using ssh. This name is typically shorter than a wiki username. It must start with a-z, and can only contain lowercase a-z, 0-9 and - characters.
The error message "There was either an authentication database error or you are not allowed to update your external account." indicates an invalid or in use shell username was provided (see T18524).