Need to dissolve glue placed intentionally in a lock
To paraphrase the link you mentioned,
Without knowing the specific glue, you should try different solvents to see if it dissolves the glue:

Start with a mild, non-polar solvent like paint thinner.
If that doesn't work, try a polar solvent like acetone.
If that doesn't work, try tetrahydrofuran (PVC pipe solvent)

All of these solvents are flammable and pretty nasty if you get them on you. To minimise risk, use small quantities at a time, minimise the time that the lid is off the container. The fumes shouldn't be too much of a problem if you're outside, but still take care.