If there is a problem installing the update, suggest that the user download a fresh copy from mendeley.com

* Centralize the error message text shown to the user in the event of a problem
   installing the update in AppInfo::updateErrorMessage() and add a section
   suggesting that the user should download a new copy from mendeley.com

src/AppInfo.cpp

@@ -52,3 +52,12 @@ std::string AppInfo::logFilePath()
 	return appDataPath(organizationName(),appName())  + '/' + "update-log.txt";
 }
 
+std::string AppInfo::updateErrorMessage(const std::string& details)
+{
+	std::string result = "There was a problem installing the update:\n\n";
+	result += details;
+	result += "\n\nYou can try downloading and installing the latest version of "
+	          "Mendeley Desktop from http://www.mendeley.com/download-mendeley-desktop";
+	return result;
+}
+

src/AppInfo.h

@@ -15,6 +15,11 @@ class AppInfo
 		static std::string organizationName();
 
 		static std::string logFilePath();
+
+		/** Returns a message to display to the user in the event
+		  * of a problem installing the update.
+		  */
+		static std::string updateErrorMessage(const std::string& details);
 };
 
 inline std::string AppInfo::name()

src/UpdateDialogGtk.cpp

@@ -103,7 +103,7 @@ gboolean UpdateDialogGtk::notify(void* _message)
 		case UpdateMessage::UpdateFailed:
 			{
 				dialog->m_hadError = true;
-				std::string errorMessage = "There was a problem installing the update:\n\n" + message->message;
+				std::string errorMessage = AppInfo::updateErrorMessage(message->message);
 				GtkWidget* errorDialog = gtk_message_dialog_new (GTK_WINDOW(dialog->m_window),
 						GTK_DIALOG_DESTROY_WITH_PARENT,
 						GTK_MESSAGE_ERROR,

src/UpdateDialogWin32.cpp

@@ -171,8 +171,7 @@ LRESULT WINAPI UpdateDialogWin32::windowProc(HWND window, UINT message, WPARAM w
 				case UpdateMessage::UpdateFailed:
 					{
 						m_hadError = true;
-						std::string text = "There was a problem installing the update:\n\n" +
-						                   message->message;
+						std::string text = AppInfo::updateErrorMessage(message->message);
 						MessageBox(m_window.GetHwnd(),text.c_str(),"Update Problem",MB_OK);
 					}
 					break;