Change: use redash.utils.json_dumps instead of json.dumps in Python query runner

[ehfeng]

Currently, python runner is returning datetime objects as unicode strings. redash.utils.json_dumps returns them as native python datetime objects.

[ehfeng]

Still figuring out how to set this up locally, so I made this change blind, based on our gitter discussion.

[arikfr]

Ping me on the chat if you want a walkthrough of the setup.

[ehfeng]

@arikfr realized this changes behavior—for hosted redash, it may be worth messaging your users, in case their old queries break.

[arikfr]

It's only an extension of the previous behavior - the data types json_dumps handles make the regular json.dumps call raise an exception.

But anyway we don't have the Python query runner enabled in the hosted version, as it's a security risk. While it runs in a sandbox, I quite easily managed to by pass it. And I'm not some hacker...

Thanks for the concern though :)

[ehfeng]

Dang, lucky. Breaking changes and migrations are always a pain :P

[arikfr]

True that 😱