bad argument #1 to 'len' (string expected, got function)? How do i fix That?

In order to show you the script i had to make it a past bin link because its having problems on here. Link:http://pastebin.com/3Lg4HkJv The Error is below were i marked it as :-- RbxApi Stuff Some Variables

-- Services
local HttpService = game:GetService("HttpService")
local ReplicatedStorage = game:GetService("ReplicatedStorage")
local ServerStorage = game:GetService("ServerStorage")
local Players = game:GetService("Players")
local Teams = game:GetService("Teams")
local Workspace = game:GetService("Workspace")
local Debris = game:GetService("Debris")
local ContentProvider = game:GetService("ContentProvider")

-- Functions
function httpGet(url)
	return game:HttpGet(url,true)
end

-- RbxApi Stuff

local apiUrl = "http://anaminus.github.io/rbx/json/api/latest.json"
local maxChunkSize = 100 * 1000
local ApiJson
if script:FindFirstChild("RawApiJson") then
	ApiJson = script.RawApiJson
else
	ApiJson = ""
end
local function getLocalApiJson()
local rawApiJson = im puting this part of the = in pastbin because too long http://pastebin.com/PxUCfrft

Main Error

local function getCurrentApiJson()
	local jsonStr = nil
	local success, err = pcall(function()
		jsonStr = HttpService:GetAsync(apiUrl)
		print("Fetched json successfully")
	end)
	if success then
		print("Returning json")
		print(jsonStr:sub(1,500))
		return jsonStr
	else
		print("Error fetching json: " .. tostring(err))
		print("Falling back to local copy")
		return getLocalApiJson()
	end
end
local function splitStringIntoChunks(jsonStr)
	-- Splits up a string into a table with a given size
	local t = {}
	for i = 1, math.ceil(string.len(jsonStr)/maxChunkSize) do
		local str = jsonStr:sub((i-1)*maxChunkSize+1, i*maxChunkSize)
		table.insert(t, str)
	end
	return t
end