fix: update unit test for go 1.14 error string change

Signed-off-by: Matt Butcher <matt.butcher@microsoft.com>

pkg/getter/httpgetter.go

@@ -18,6 +18,7 @@ package getter
 import (
 	"bytes"
 	"crypto/tls"
+	"fmt"
 	"io"
 	"net/http"
 
@@ -67,7 +68,10 @@ func (g *HTTPGetter) get(href string) (*bytes.Buffer, error) {
 
 	resp, err := client.Do(req)
 	if err != nil {
-		return buf, err
+		// In Go 1.14, the error returned from client.Do changed.
+		// This is for backward compatibility, so that tests will pass
+		// for Go 1.13 and before as well as 1.14 and beyond.
+		return buf, fmt.Errorf("Get %s: %s", href, err)
 	}
 	if resp.StatusCode != 200 {
 		return buf, errors.Errorf("failed to fetch %s : %s", href, resp.Status)