build: retry PPA upload up to three times (#31099)

build/ci.go

@@ -883,11 +883,17 @@ func ppaUpload(workdir, ppa, sshUser string, files []string) {
 			os.WriteFile(idfile, sshkey, 0600)
 		}
 	}
-	// Upload
+	// Upload. This doesn't always work, so try up to three times.
 	dest := sshUser + "@ppa.launchpad.net"
-	if err := build.UploadSFTP(idfile, dest, incomingDir, files); err != nil {
-		log.Fatal(err)
+	for i := 0; i < 3; i++ {
+		err := build.UploadSFTP(idfile, dest, incomingDir, files)
+		if err == nil {
+			return
+		}
+		log.Println("PPA upload failed:", err)
+		time.Sleep(5 * time.Second)
 	}
+	log.Fatal("PPA upload failed all attempts.")
 }
 
 func getenvBase64(variable string) []byte {