made fs.cp fail if either handle fails to open. ???

modules/lib/fs.lua

@@ -236,9 +236,13 @@ end
 function fs.cp(s,d)
  local df = fs.open(d,"wb")
  local sf = fs.open(s,"rb")
- fs.write(df,fs.readall(sf))
- fs.close(df)
- fs.close(sf)
+ if df and sf then
+  fs.write(df,fs.readall(sf))
+  fs.close(df)
+  fs.close(sf)
+  return true
+ end
+ return false
 end
 function fs.mv(s,d)
  fs.cp(s,d)