Add backtrace to error function

builtin/builtin.lua

@@ -10,6 +10,12 @@ print = minetest.debug
 math.randomseed(os.time())
 os.setlocale("C", "numeric")
 
+local errorfct = error
+error = function(text)
+	print(debug.traceback(""))
+	errorfct(text)
+end
+
 -- Load other files
 local modpath = minetest.get_modpath("__builtin")
 dofile(modpath.."/serialize.lua")

builtin/mainmenu.lua

@@ -2,6 +2,12 @@ print = engine.debug
 math.randomseed(os.time())
 os.setlocale("C", "numeric")
 
+local errorfct = error
+error = function(text)
+	print(debug.traceback(""))
+	errorfct(text)
+end
+
 local scriptpath = engine.get_scriptdir()
 
 mt_color_grey  = "#AAAAAA"