worker/clienterrors: add empty packagespec error

Add an error case for an empty package spec returned
by a depsolve job and mark this with a `4xx` status.

internal/cloudapi/v2/server.go

@@ -283,6 +283,11 @@ func generateManifest(ctx context.Context, workers *worker.Server, depsolveJobID
 		return
 	}
 
+	if len(depsolveResults.PackageSpecs) == 0 {
+		jobResult.JobError = clienterrors.WorkerClientError(clienterrors.ErrorEmptyPackageSpecs, "Received empty package specs")
+		return
+	}
+
 	manifest, err := imageType.Manifest(b, options, repos, depsolveResults.PackageSpecs, seed)
 	if err != nil {
 		reason := "Error generating manifest"

internal/worker/clienterrors/errors.go

@@ -21,10 +21,11 @@ const (
 	ErrorOldResultCompatible  ClientErrorCode = 18
 	ErrorEmptyManifest        ClientErrorCode = 19
 
-	ErrorDNFDepsolveError ClientErrorCode = 20
+	ErrorDNFDepsolveError  ClientErrorCode = 20
-	ErrorDNFMarkingErrors ClientErrorCode = 21
+	ErrorDNFMarkingErrors  ClientErrorCode = 21
-	ErrorDNFOtherError    ClientErrorCode = 22
+	ErrorDNFOtherError     ClientErrorCode = 22
-	ErrorRPMMDError       ClientErrorCode = 23
+	ErrorRPMMDError        ClientErrorCode = 23
+	ErrorEmptyPackageSpecs ClientErrorCode = 24
 )
 
 type ClientErrorCode int
@@ -68,6 +69,8 @@ func GetStatusCode(err *Error) StatusCode {
 		return JobStatusUserInputError
 	case ErrorManifestDependency:
 		return JobStatusUserInputError
+	case ErrorEmptyPackageSpecs:
+		return JobStatusUserInputError
 	case ErrorEmptyManifest:
 		return JobStatusUserInputError
 	default: