Handle cases where GitHub release does not exist for tag

tools/version-tracker/pkg/github/github.go

@@ -3,6 +3,7 @@ package github
 import (
 	"context"
 	"encoding/base64"
+	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -19,6 +20,8 @@ import (
 	"github.com/aws/eks-anywhere-build-tooling/tools/version-tracker/pkg/util/version"
 )
 
+var ErrNotFound = errors.New("404 Not Found")
+
 // getTagsForRepo retrieves the list of tags for the given GitHub repository.
 func getTagsForRepo(client *github.Client, org, repo string) ([]*github.RepositoryTag, error) {
 	logger.V(6).Info(fmt.Sprintf("Getting tags for [%s/%s] repository", org, repo))
@@ -149,10 +152,17 @@ func GetLatestRevision(client *github.Client, org, repo, currentRevision string,
 				}
 			}
 			releaseForTag, _, err := client.Repositories.GetReleaseByTag(context.Background(), org, repo, tagName)
+			preRelease := false
 			if err != nil {
-				return "", false, fmt.Errorf("calling GetReleaseByTag API for tag %s in [%s/%s] repository: %v", tagName, org, repo, err)
+				if err == ErrNotFound {
+					preRelease = false
+				} else {
+					return "", false, fmt.Errorf("calling GetReleaseByTag API for tag %s in [%s/%s] repository: %v", tagName, org, repo, err)
+				}
+			} else {
+				preRelease = *releaseForTag.Prerelease
 			}
-			if *releaseForTag.Prerelease {
+			if preRelease {
 				continue
 			}