bpo-40334: Improve column offsets for thrown syntax errors by Pegen

[isidentical]

I've been trying to figure out a good way to handle ast.c errors, but no luck so far. I've splitted them to their own test and fixed remaining offset errors to ensure full compatibility with the old parser.

https://bugs.python.org/issue40334

[lysnikolaou]

Thanks @isidentical for spending time on this! It's a really nice improvement.

[gvanrossum]

@isidentical there's a merge conflict -- you need to merge master and run make regen-pegen. Then I'm good with merging this.

[isidentical]

@gvanrossum resolved

[pablogsal]

+77 −109

Best way of fixing a bug! 🎉

[pablogsal]

The travis target is stucked, closing and reopening to re-trigger the CI

[pablogsal]

Hummm, there is a bunch of warnings now after the last rebasing:

/home/travis/build/python/cpython/Parser/pegen/pegen.h:194:59: warning: incompatible pointer to integer conversion passing 'char [45]' to parameter of type 'int' [-Wint-conversion]
        return _PyPegen_raise_error(p, PyExc_SyntaxError, "%s only supported in Python 3.%i and greater",
                                                          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

@isidentical could you take a look? Seems that we are passing the error message incorrectly with this PR

[isidentical]

Seems that we are passing the error message incorrectly with this PR

Yup, this PR changes signature of _PyPegen_raise_error. I missed that usage when I rebased. Now, it should be fixed.