more fiddling with string.rep

sandbox.lua

@@ -54,10 +54,12 @@ local function run(f, options)
   string.rep = nil
 
   setfenv(f, BASE_ENV)
-  local result = f()
+  local ok, result = pcall(f)
 
   string.rep = string_rep
 
+  if not ok then error(result) end
+
   return result
 end