Updated common/download.go to handle when a connection error happens (response is nil), and reformatted the error that's returned when an HTTP error occurs.

common/download.go

@@ -278,12 +278,24 @@ func (d *HTTPDownloader) Download(dst *os.File, src *url.URL) error {
 	}
 
 	resp, err := httpClient.Do(req)
-	if err != nil {
-		log.Printf("[DEBUG] (download) Error making HTTP HEAD request: %s", err.Error())
+	if err != nil || resp == nil {
+
+		if resp == nil {
+			log.Printf("[DEBUG] (download) HTTP connection error: %s", err.Error())
+
+		} else if resp.StatusCode >= 400 && resp.StatusCode < 600 {
+			log.Printf("[DEBUG] (download) Non-successful HTTP status code (%s) while making HEAD request: %s", resp.Status, err.Error())
+
+		} else {
+			log.Printf("[DEBUG] (download) Error making HTTP HEAD request (%s): %s", resp.Status, err.Error())
+		}
+
 	} else {
+
 		if resp.StatusCode >= 200 && resp.StatusCode < 300 {
 			// If the HEAD request succeeded, then attempt to set the range
 			// query if we can.
+
 			if resp.Header.Get("Accept-Ranges") == "bytes" {
 				if fi, err := dst.Stat(); err == nil {
 					if _, err = dst.Seek(0, os.SEEK_END); err == nil {
@@ -293,6 +305,7 @@ func (d *HTTPDownloader) Download(dst *os.File, src *url.URL) error {
 					}
 				}
 			}
+
 		} else {
 			log.Printf("[DEBUG] (download) Unexpected HTTP response during HEAD request: %s", resp.Status)
 		}
@@ -302,12 +315,17 @@ func (d *HTTPDownloader) Download(dst *os.File, src *url.URL) error {
 	req.Method = "GET"
 
 	resp, err = httpClient.Do(req)
-	if err != nil {
-		return err
-	} else {
-		if resp.StatusCode >= 400 && resp.StatusCode < 600 {
-			return fmt.Errorf("Error making HTTP GET request: %s", resp.Status)
+	if err == nil && (resp.StatusCode >= 400 && resp.StatusCode < 600) {
+		return fmt.Errorf("Error making HTTP GET request: %s", resp.Status)
+
+	} else if err != nil {
+		if resp == nil {
+			return fmt.Errorf("HTTP connection error: %s", err.Error())
+
+		} else if resp.StatusCode >= 400 && resp.StatusCode < 600 {
+			return fmt.Errorf("HTTP %s error: %s", resp.Status, err.Error())
 		}
+		return fmt.Errorf("HTTP error: %s", err.Error())
 	}
 
 	d.total = d.current + uint64(resp.ContentLength)