I tried to migrate to 7.3 using the steps provided above - and all seemed to be working swimmingly until it errored out with "ECONNRESET" importing the mysql DB.
It's a very large mysql DB (5.8 GB). Any idea why the connection might reset (the backup is on a linode volume connected to the local filesystem)? Or a way to go about upgrading this app without hitting the same error again?
EDIT: To make matters worse, I also can't uninstall the app where I tried to do the upgrade for likely the same reason. Error was: " Error : Addons Error - Error tearing down mysql: socket hang up "
EDIT 2: I resolved, at least the uninstall problem, by allocating more RAM to mysql. Seeing if that solves the over all problem now!