Hubzilla-Dokumentation:

Inhalt

check_account_password

Use this hook to provide additional checks or validations of the password given when
registering and account.

Arguments:

array(
    'password' => $password,    // The password to check
    'result' => array(
        'error' => false,
        'message' => ''
    )
)

Results:

For a failed check set the error member of the result
array to true and the message to a short message
explaining why it failed.

Otherwise, leave it alone.