Print libcurl error buffer to stderr on client error

src/client/http/Request.cpp

@@ -159,6 +159,9 @@ namespace http
 			curl_easy_setopt(easy, CURLOPT_FOLLOWLOCATION, 1L);
 			curl_easy_setopt(easy, CURLOPT_MAXREDIRS, 10L);
 
+			curl_easy_setopt(easy, CURLOPT_ERRORBUFFER, error_buffer);
+			error_buffer[0] = 0;
+
 			curl_easy_setopt(easy, CURLOPT_TIMEOUT, timeout);
 			curl_easy_setopt(easy, CURLOPT_HTTPHEADER, headers);
 			curl_easy_setopt(easy, CURLOPT_URL, uri.c_str());

src/client/http/Request.h

@@ -25,6 +25,7 @@ namespace http
 		ByteString response_body;
 
 		CURL *easy;
+		char error_buffer[CURL_ERROR_SIZE];
 
 		volatile curl_off_t rm_total;
 		volatile curl_off_t rm_done;

src/client/http/RequestManager.cpp

@@ -3,6 +3,8 @@
 #include "Config.h"
 #include "Platform.h"
 
+#include <iostream>
+
 const int curl_multi_wait_timeout_ms = 100;
 const long curl_max_host_connections = 6;
 
@@ -142,6 +144,11 @@ namespace http
 							break;
 						}
 
+						if (finish_with >= 600)
+						{
+							std::cerr << request->error_buffer << std::endl;
+						}
+
 						request->status = finish_with;
 					}
 				};