[FAB-7880] add error code to empty cert

	clients can now verify the empty cert error code from the sdk.
	This is used when calling TLSCACerts.TLSCert() on the orderer
	or the peer's config.

	to check if an empty cert is returned cast it to a status object
	and verify its code. Example:
	ocert, err := ordererConfig.TLSCACerts.TLSCert()
	s, ok := status.FromError(err)
	if ok && s.code == status.EmptyCert.ToInt32() {
	// then we have an empty cert error
	}

Change-Id: Ibe4e68c478bd95d2930a8001b68ef81352dc3b45
Signed-off-by: Baha Shaaban <baha.shaaban@securekey.com>

api/apiconfig/network.go

@@ -12,6 +12,7 @@ import (
 	"io/ioutil"
 
 	"github.com/hyperledger/fabric-sdk-go/pkg/errors"
+	"github.com/hyperledger/fabric-sdk-go/pkg/status"
 )
 
 // NetworkConfig provides a static definition of a Hyperledger Fabric network
@@ -184,7 +185,8 @@ func loadCert(rawData []byte) (*x509.Certificate, error) {
 		return pub, nil
 	}
 
-	return nil, errors.New("pem data missing")
+	// return an error with an error code for clients to test against status.EmptyCert code
+	return nil, status.New(status.ClientStatus, status.EmptyCert.ToInt32(), "pem data missing", nil)
 }
 
 // MutualTLSConfig Mutual TLS configurations

pkg/status/codes.go

@@ -29,6 +29,9 @@ const (
 
 	// EndorsementMismatch is returned when there is a mismatch in endorsements received by the SDK
 	EndorsementMismatch Code = 3
+
+	// EmptyCert is return when an empty cert is returned
+	EmptyCert Code = 4
 )
 
 // CodeName maps the codes in this packages to human-readable strings
@@ -37,6 +40,7 @@ var CodeName = map[int32]string{
 	1: "UNKNOWN",
 	2: "CONNECTION_FAILED",
 	3: "ENDORSEMENT_MISMATCH",
+	4: "EMPTY_CERT",
 }
 
 // ToInt32 cast to int32

pkg/status/status.go

@@ -69,6 +69,8 @@ const (
 	EndorserClientStatus
 	// OrdererClientStatus status returned from the orderer client
 	OrdererClientStatus
+	// ClientStatus is a generic client status
+	ClientStatus
 )
 
 // GroupName maps the groups in this packages to human-readable strings
@@ -82,6 +84,7 @@ var GroupName = map[int32]string{
 	6: "Fabric CA Server Status",
 	7: "Endorser Client Status",
 	8: "Orderer Client Status",
+	9: "Client Status",
 }
 
 func (g Group) String() string {
@@ -120,7 +123,7 @@ func (s *Status) codeString() string {
 		return ToFabricCommonStatusCode(s.Code).String()
 	case EventServerStatus:
 		return ToTransactionValidationCode(s.Code).String()
-	case EndorserClientStatus, OrdererClientStatus:
+	case EndorserClientStatus, OrdererClientStatus, ClientStatus:
 		return ToSDKStatusCode(s.Code).String()
 	default:
 		return Unknown.String()