Deprecate tabs for indenting (was Re: Indenting with tabs vs spaces)

[Fredrik Lundh]

Ville Vainio wrote:

> Why don't issue a DeprecationWarning whenever tabs are found in the
> source file? That wouldn't "break" things, but it would surely
> motivate tab-using people to learn the right way of doing things.

why not issue a WhitespaceTrollWarning whenever your name
is found in Python source code?  Sure wouldn't break any of my
code.