Include validator that would automatically check compliance of code

[matkoniecz]

Ideally, it would be something that can be pointed at files on disk or on deployed website.

Somethings may be tricky, but some should be relatively easy.

I have quite clunky code at https://github.com/matkoniecz/mapsaregreat.com/blob/master/code%20and%20content%20not%20served%20directly/custom_validator.py#L173 and was quite surprised that such validator does not really exist.