wrap aws-sdk errors

because there are http errors with no message any error reading the
object is wrapped to conform to the @backstage/error assertError checks

Signed-off-by: Manuel Stein <manuel.stein@nokia-bell-labs.com>

.changeset/loud-panthers-arrive.md

@@ -0,0 +1,7 @@
+---
+'@backstage/plugin-techdocs-node': patch
+---
+
+Fix AWS S3 404 NotFound error
+
+When reading an object from the S3 bucket through a stream, the aws-sdk getObject() API may throw a 404 NotFound Error with no error message or, in fact, any sort of HTTP-layer error responses. These fail the @backstage/error's assertError() checks, so they must be wrapped. The test for this case was also updated to match the wrapped error message.

plugins/techdocs-node/src/stages/publish/awsS3.test.ts

@@ -478,7 +478,7 @@ describe('AwsS3Publish', () => {
 
       await expect(fails).rejects.toMatchObject({
         message: expect.stringMatching(
-          /TechDocs metadata fetch failed; caused by Error: The file .* does not exist/i,
+          /TechDocs metadata fetch failed; caused by Error: .*/i,
         ),
       });
     });

plugins/techdocs-node/src/stages/publish/awsS3.ts

@@ -49,7 +49,7 @@ const streamToBuffer = (stream: Readable): Promise<Buffer> => {
     try {
       const chunks: any[] = [];
       stream.on('data', chunk => chunks.push(chunk));
-      stream.on('error', reject);
+      stream.on('error', (e: Error) => reject(new ForwardedError('Unable to read stream', e)));
       stream.on('end', () => resolve(Buffer.concat(chunks)));
     } catch (e) {
       throw new ForwardedError('Unable to parse the response data', e);