This adds package errors, which provides error handling constructs that are
specific to the protobuf repo. In particular, it provides a NonFatal type
which is useful for capturing non-fatal errors like invalid UTF-8 and required
fields not set.
High-level API:
type NonFatalErrors []error
func (NonFatalErrors) Error() string
type NonFatal struct{ ... }
func (*NonFatal) Merge(err error) (ok bool)
func (*NonFatal) AppendInvalidUTF8(field string)
func (*NonFatal) AppendRequiredNotSet(field string)
func New(string, ...interface{}) error
Change-Id: I9448c586008240e8987573fe79e0ffb024e7629d
Reviewed-on: https://go-review.googlesource.com/127338
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-by: Herbie Ong <herbie@google.com>
