Ignore extra error tokens.

[wenovus]

An alternative that fixes #116.

This is essentially what @pborman proposed in #117 (comment).

I wasn't able to reproduce test failing as mentioned by @andaru in #117 (comment) in the current codebase, so pborman's suggestion now makes more sense.

The reason seems to be that error tokens are always skipped, so they don't seem to affect Location as Andrew mentioned:

goyang/pkg/yang/parse.go

Lines 207 to 214 in 1fb7893

	// next returns the next unprocessed lexer token.
	next := func() *token {
	for {
	if t := p.lex.NextToken(); t.Code() != tError {
	return t
	}
	}
	}

[coveralls]

Coverage increased (+0.2%) to 81.768% when pulling a22c8a0 on ignore-too-many-errors into 1fb7893 on master.

[robshakir]

Thanks - I'm not sure that we ever properly reproduced this issue -- but this looks to handle the invalid escapes that were being discussed.