bpo-36948: Fix NameError in urllib.request.URLopener.retrieve (GH-13389)

diff --git a/Lib/urllib/request.py b/Lib/urllib/request.py
index df2ff06..230ac39 100644
--- a/Lib/urllib/request.py
+++ b/Lib/urllib/request.py
@@ -1783,7 +1783,7 @@
                 fp = self.open_local_file(url1)
                 hdrs = fp.info()
                 fp.close()
-                return url2pathname(splithost(url1)[1]), hdrs
+                return url2pathname(_splithost(url1)[1]), hdrs
             except OSError as msg:
                 pass
         fp = self.open(url, data)
@@ -1792,10 +1792,10 @@
             if filename:
                 tfp = open(filename, 'wb')
             else:
-                garbage, path = splittype(url)
-                garbage, path = splithost(path or "")
-                path, garbage = splitquery(path or "")
-                path, garbage = splitattr(path or "")
+                garbage, path = _splittype(url)
+                garbage, path = _splithost(path or "")
+                path, garbage = _splitquery(path or "")
+                path, garbage = _splitattr(path or "")
                 suffix = os.path.splitext(path)[1]
                 (fd, filename) = tempfile.mkstemp(suffix)
                 self.__tempfiles.append(filename)