local stack_trace = debug.traceback('Error: ' .. tostring(err), --[[stack frame]]2):gsub('\n[^\n]+$', '')
  app.send_run_time_error(stack_trace)
  Error_message = 'Something is wrong. Sorry!\n\n'..stack_trace..'\n\n'..

  local callstack = debug.traceback('', --[[stack frame]]2)
  local cleaned_up_error = 'Error: ' .. cleaned_up_frame(tostring(err))..'\n'..cleaned_up_callstack(callstack)
  app.send_run_time_error(cleaned_up_error)
  Error_message = 'Something is wrong. Sorry!\n\n'..cleaned_up_error..'\n\n'..

-- I tend to read code from files myself (say using love.filesystem calls)
-- rather than offload that to load().
-- Functions compiled in this manner have ugly filenames of the form [string "filename"]
-- This function cleans out this cruft from error callstacks.
-- It also strips out the numeric prefixes we introduce in filenames.
function cleaned_up_callstack(callstack)
  local frames = {}
  for frame in string.gmatch(callstack, '[^\n]+\n*') do
    table.insert(frames, cleaned_up_frame(frame))
  end
  -- the initial "stack traceback:" line was unindented and remains so
  return table.concat(frames, '\n\t')
end
function cleaned_up_frame(frame)
  local line = frame:gsub('^%s*(.-)\n?$', '%1')
  local filename, rest = line:match('([^:]*):(.*)')
  return cleaned_up_filename(filename)..':'..rest
end
function cleaned_up_filename(filename)
  -- pass through frames that don't match this format
  -- this includes the initial line "stack traceback:"
  local core_filename = filename:match('^%[string "(.*)"%]$')
  if core_filename == nil then return filename end
  -- strip out the numeric prefixes we introduce in filenames
  local _, core_filename2 = core_filename:match('^(%d+)-(.+)')
  return core_filename2 or core_filename
end