This time with a version constrain that should allow this to expire at
some point in the future.

Title: GnuCash 2.7+ Breaking Change
Author: Aaron W. Swenson <titanofold@gentoo.org>
Posted: 2018-01-11
Revision: 1
News-Item-Format: 2.0
Display-If-Installed: <app-office/gnucash-4

Along with changes to use modern libraries, GnuCash 2.7+ has changed the
schema [1] it uses for both databases and files. GnuCash will
automatically modify the file or database in place upon open.

Therefore, it is imperative that you back up any files or databases
before using GnuCash 2.7 in case you run into an issue and want or need
to revert back to 2.6.

Instructions for backing up are as follows:

For XML (plain files):
$ cp /path/to/file.gnucash /path/to/file.gnucash.bak

For MySQL:
$ mysqldump gnucash_db | mysql gnucash_db_bak

For PostgreSQL:
$ createdb -U dbadmin -T gnucash_db -O gnucash_user gnucash_db_bak

For SQLite:
$ cp /path/to/gnucash/sqlite.file.gnucash /path/to/gnucash/sqlite.file.gnucash.bak

[1] https://github.com/Gnucash/gnucash/releases/tag/2.7.0a