consistent promise behavior for upload artifact

packages/artifact/src/internal/shared/errors.ts

@@ -0,0 +1,21 @@
+export class FilesNotFoundError extends Error {
+  files: string[]
+
+  constructor(files: string[] = []) {
+    let message = 'No files were found to upload'
+    if (files.length > 0) {
+      message += `: ${files.join(', ')}`
+    }
+
+    super(message)
+    this.files = files
+    this.name = 'FilesNotFoundError'
+  }
+}
+
+export class InvalidResponseError extends Error {
+  constructor(message: string) {
+    super(message)
+    this.name = 'InvalidResponseError'
+  }
+}