Return filestore.ErrNotFound when object not found

[sanposhiho]

What this PR does / why we need it:

Currently, minio client gives back no error even if the given object not found when GetObject called.
We should treat as filestore.ErrNotFound like GCS. If we don't, the caller cannot handle it properly:

Which issue(s) this PR fixes:

Fixes #1309

Does this PR introduce a user-facing change?:

NONE

[pipecd-bot]

Code coverage for golang is 33.81%. This pull request does not change code coverage.

[nakabonne]

nit: It would be great if it could be followed our style where must be indented if multiple args given:

	s.logger.Error("failed to create minio object reader",
		zap.String("path", path),
		zap.Error(err),
	)

[nghialv]

Thank you.
/approve

[pipecd-bot]

The following files are not gofmt-ed. By commenting /golinter fmt, the formatted one will be appended to this pull request automatically.

pkg/filestore/minio/minio.go

--- pkg/filestore/minio/minio.go.orig
+++ pkg/filestore/minio/minio.go
@@ -106,7 +106,7 @@
 		if e.StatusCode == http.StatusNotFound {
 			err = filestore.ErrNotFound
 		}
-		s.logger.Error("failed to stat minio object", 
+		s.logger.Error("failed to stat minio object",
 			zap.String("path", path),
 			zap.Error(err),
 		)

[sanposhiho]

/golinter fmt

[nghialv]

/approve

[pipecd-bot]

Code coverage for golang is 33.81%. This pull request does not change code coverage.

[nghialv]

/approve

[pipecd-bot]

This pull request is APPROVED by nghialv.

Approvers can cancel the approval by writing /approve cancel in a comment. Any additional commits also will change this pull request to be not-approved.