Merge branch 'master' into jgrpp

# Conflicts:
#	src/error.h
#	src/error_gui.cpp
#	src/linkgraph/linkgraph_gui.cpp
#	src/misc_gui.cpp
#	src/newgrf_gui.cpp
#	src/news_gui.cpp
#	src/rail_cmd.cpp
#	src/saveload/gamelog_sl.cpp
#	src/script/api/script_text.cpp
#	src/script/script_instance.cpp
#	src/statusbar_gui.cpp
#	src/strings.cpp
#	src/strings_func.h
#	src/strings_internal.h
#	src/table/settings/gui_settings.ini
#	src/table/settings/linkgraph_settings.ini
#	src/textbuf_gui.h

src/bootstrap_gui.cpp

@@ -262,6 +262,14 @@ public:
 
 	void OnConnect(bool success) override
 	{
+		if (!success) {
+			usererror("Failed to connect to content server. Please acquire a graphics set for OpenTTD. See section 1.4 of README.md.");
+			/* _exit_game is used to break out of the outer video driver's MainLoop. */
+			_exit_game = true;
+			this->Close();
+			return;
+		}
+
 		/* Once connected, request the metadata. */
 		_network_content_client.RequestContentList(CONTENT_TYPE_BASE_GRAPHICS);
 	}