Flask people
so I was given this old flask project, around 3k lines written in py2, the code is simply old and not refactored. So, it's pile of shit. Migrations completely botched as the original author created reference to live data in models.
Very strict line formatting resulting in backslashed ternary conditions.
Even saw manually formatted json responses... _line by line_.

My job is to clean this mess and eventually do as much as possible to freshen the whole project.
Currently just refucktoring the code as it's the only easy thing to do out of everything that could be done (it's still slow process).

Any tricks and tips? currently considering to try upgrading it to py3 but it feels like throwing gunpowder into already burning house.

Large coffee, light German electronica. Legacy code, here I go!