MySQL migration not possible on MariaDB included with Debian stable.

[simonszu]

Hi,
i have already opened an issue on the container project, since it occured when i worked with the container, but i believe it is better suitable for the codebase of codimd. Check this out: hedgedoc/container#7

[SISheogorath]

I guess this will be resolved when #873 is solved.

But if someone wants to investigate it for version 3 feel free to do so :)