test: update test_unicode_file

Lib/test/test_unicode_file.py

@@ -2,16 +2,17 @@
 # We don't test many operations on files other than
 # that their names can be used with Unicode characters.
 import os, glob, time, shutil
+import sys
 import unicodedata
 
 import unittest
-from test.support import run_unittest
 from test.support.os_helper import (rmtree, change_cwd, TESTFN_UNICODE,
     TESTFN_UNENCODABLE, create_empty_file)
 
+
 if not os.path.supports_unicode_filenames:
     try:
-        TESTFN_UNICODE.encode(TESTFN_ENCODING)
+        TESTFN_UNICODE.encode(sys.getfilesystemencoding())
     except (UnicodeError, TypeError):
         # Either the file system encoding is None, or the file name
         # cannot be encoded in the file system encoding.
@@ -134,8 +135,6 @@ class TestUnicodeFiles(unittest.TestCase):
             self._do_directory(TESTFN_UNENCODABLE+ext,
                                TESTFN_UNENCODABLE+ext)
 
-def test_main():
-    run_unittest(__name__)
 
 if __name__ == "__main__":
-    test_main()
+    unittest.main()