only check listdir on dirs

is_hidden is called with files, not just dirs

IPython/html/utils.py

@@ -102,10 +102,12 b" def is_hidden(abs_path, abs_root=''):"
     if any(part.startswith('.') for part in inside_root.split(os.sep)):
         return True
 
-    # check that path can be listed
+    # check that dirs can be listed
+    # may fail on Windows junctions or non-user-readable dirs
+    if os.path.isdir(abs_path):
     try:
         os.listdir(abs_path)
-    except Exception:
+        except OSError:
         return True
     
     # check UF_HIDDEN on any location up to root
@@ -114,7 +116,7 b" def is_hidden(abs_path, abs_root=''):"
         try:
             # may fail on Windows junctions
             st = os.stat(path)
-        except Exception:
+        except OSError:
             return True
         if getattr(st, 'st_flags', 0) & UF_HIDDEN:
             return True