sql-update-3.0.0-to-combined-mysql.sh does not work at all. The first command it tries to execute is:
ALTER TABLE $TABLE MODIFY COLUMN c_location integer NULL;
yet it is impossible to convert VARCHAR like "mysql://user:pass@host:port/database/table" to INT.

Script for Postgres drops the NOT NULL constraint instead:
ALTER TABLE $TABLE ALTER COLUMN c_location DROP NOT NULL;

So I assume it should be something like:
ALTER TABLE $TABLE MODIFY COLUMN c_location VARCHAR(2048) NULL;