Add tag name to error messages

[fmeum]

Before this change, the error only included the location of the tag.

[fmeum]

What do you think, should we also add the extension ID to the error message?

[Wyverald]

Does it matter much? Shouldn't the location tell you what tag it was?

[fmeum]

Does it matter much? Shouldn't the location tell you what tag it was?

It does, but since this is an error without a Starlark stacktrace, it basically requires you to open up that file at that line before you can make sense of the error.

I guess this could be compared to a compiler error telling you that a parameter type is wrong, but not telling you the name of the function.

[fmeum]

CI is green now