Fixed tests on Windows for issue #21883.

Lib/ntpath.py

@@ -584,7 +584,7 @@ def relpath(path, start=None):
         if not rel_list:
             return curdir
         return join(*rel_list)
-    except (TypeError, ValueError, AttributeError, BytesWarning):
+    except (TypeError, ValueError, AttributeError, BytesWarning, DeprecationWarning):
         genericpath._check_arg_types('relpath', path, start)
         raise
 

Lib/posixpath.py

@@ -452,6 +452,6 @@ def relpath(path, start=None):
         if not rel_list:
             return curdir
         return join(*rel_list)
-    except (TypeError, AttributeError, BytesWarning):
+    except (TypeError, AttributeError, BytesWarning, DeprecationWarning):
         genericpath._check_arg_types('relpath', path, start)
         raise

Lib/test/test_genericpath.py

@@ -453,7 +453,8 @@ class CommonTest(GenericTest):
 
     def test_relpath_errors(self):
         # Check relpath() raises friendly TypeErrors.
-        with support.check_warnings(('', BytesWarning), quiet=True):
+        with support.check_warnings(('', (BytesWarning, DeprecationWarning)),
+                                    quiet=True):
             errmsg = "Can't mix strings and bytes in path components"
             with self.assertRaisesRegex(TypeError, errmsg):
                 self.pathmodule.relpath(b'bytes', 'str')