[#214] object: Implement Get\Head requests for EC object

Signed-off-by: Anton Nikiforov <an.nikiforov@yadro.com>

object/error.go

@@ -17,3 +17,21 @@ func (s *SplitInfoError) SplitInfo() *SplitInfo {
 func NewSplitInfoError(v *SplitInfo) *SplitInfoError {
 	return &SplitInfoError{si: v}
 }
+
+type ECInfoError struct {
+	ei *ECInfo
+}
+
+const ecInfoErrorMsg = "object not found, ec info has been provided"
+
+func (e *ECInfoError) Error() string {
+	return ecInfoErrorMsg
+}
+
+func (e *ECInfoError) ECInfo() *ECInfo {
+	return e.ei
+}
+
+func NewECInfoError(v *ECInfo) *ECInfoError {
+	return &ECInfoError{ei: v}
+}