From f0e3431bc7c2ef3ab5834b1fa36e7a8d1e99184d Mon Sep 17 00:00:00 2001
From: Alexander Alekhin <alexander.alekhin@intel.com>
Date: Wed, 21 Jun 2017 19:03:17 +0300
Subject: [PATCH 1/2] .gitignore: added ".cache" directory back

It is necessary for proper work of "git clean" command
---
 .gitignore | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.gitignore b/.gitignore
index c1b1fe642f..89c7530039 100644
--- a/.gitignore
+++ b/.gitignore
@@ -21,3 +21,4 @@ bin/
 *.log
 *.tlog
 build
+.cache

From d29c299cdbcec49470f65dab767bd433ad9f1720 Mon Sep 17 00:00:00 2001
From: Alexander Alekhin <alexander.alekhin@intel.com>
Date: Wed, 21 Jun 2017 19:04:27 +0300
Subject: [PATCH 2/2] cmake: additional messages on download errors

---
 cmake/OpenCVDownload.cmake | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/cmake/OpenCVDownload.cmake b/cmake/OpenCVDownload.cmake
index 76151bb8ed..67a416cb4b 100644
--- a/cmake/OpenCVDownload.cmake
+++ b/cmake/OpenCVDownload.cmake
@@ -167,7 +167,28 @@ function(ocv_download)
         set(${DL_STATUS} FALSE PARENT_SCOPE)
         set(msg_level WARNING)
       endif()
-      message(${msg_level} "${__msg_prefix}Download failed: ${status}")
+      if(status MATCHES "Couldn't resolve host name")
+        message(STATUS "
+=======================================================================
+  Couldn't download files from the Internet.
+  Please check the Internet access on this host.
+=======================================================================
+")
+      elseif(status MATCHES "Couldn't connect to server")
+        message(STATUS "
+=======================================================================
+  Couldn't connect to server from the Internet.
+  Perhaps direct connections are not allowed in the current network.
+  To use proxy please check/specify these environment variables:
+  - http_proxy/https_proxy
+  - and/or HTTP_PROXY/HTTPS_PROXY
+=======================================================================
+")
+      endif()
+      message(${msg_level} "${__msg_prefix}Download failed: ${status}
+For details please refer to the download log file:
+${OPENCV_DOWNLOAD_LOG}
+")
       return()
     endif()