pylint #9386 don't issue "unable to import module" when in try: except ImportError [open]

try:
  import io
except ImportError:
  try:
      import cStringIO as io
  except ImportError:
      import StringIO as io

However pylint complains about one or another module being not importable:

F:  7: Unable to import 'io' (No module named io)
prioritynormal
typeenhancement
done in<not specified>
load0.500
load left0.500
closed by<not specified>