Add error case for Error JSON parsing (#21)

error.go

@@ -1,12 +1,14 @@
 package reggie
 
-import (
-	spec "github.com/opencontainers/distribution-spec/specs-go/v1"
-)
-
 type (
+	ErrorResponse struct {
+		Errors []ErrorInfo `json:"errors"`
+	}
+
 	// ErrorInfo describes a server error returned from a registry.
 	ErrorInfo struct {
-		*spec.ErrorInfo
+		Code    string `json:"code"`
+		Message string `json:"message"`
+		Detail  interface{} `json:"detail"`
 	}
 )

response.go

@@ -2,11 +2,11 @@ package reggie
 
 import (
 	"encoding/json"
+	"errors"
 	"net/http"
 	"net/url"
 
 	"github.com/go-resty/resty/v2"
-	spec "github.com/opencontainers/distribution-spec/specs-go/v1"
 )
 
 type (
@@ -46,15 +46,17 @@ func (resp *Response) IsUnauthorized() bool {
 
 // Errors attempts to parse a response as OCI-compliant errors array
 func (resp *Response) Errors() ([]ErrorInfo, error) {
-	errorResponse := &spec.ErrorResponse{}
+	errorResponse := &ErrorResponse{}
 	bodyBytes := []byte(resp.String())
 	err := json.Unmarshal(bodyBytes, errorResponse)
 	if err != nil {
 		return nil, err
+	} else if len(errorResponse.Errors) == 0 {
+		return nil, errors.New("body was valid json but could not be parsed")
 	}
 	errorList := []ErrorInfo{}
 	for _, errorInfo := range errorResponse.Errors {
-		errorList = append(errorList, ErrorInfo{&errorInfo})
+		errorList = append(errorList, errorInfo)
 	}
 	return errorList, nil
 }