Test for UnicodeError instead of ImportError to determine whether

the test file name can be encoded.

Lib/test/test_unicode_file.py

@@ -7,7 +7,7 @@ from test.test_support import verify, TestSkipped, TESTFN_UNICODE
 from test.test_support import TESTFN_ENCODING
 try:
     TESTFN_ENCODED = TESTFN_UNICODE.encode(TESTFN_ENCODING)    
-except (ImportError, TypeError):
+except (UnicodeError, TypeError):
     # Either the file system encoding is None, or the file name
     # cannot be encoded in the file system encoding.
     raise TestSkipped("No Unicode filesystem semantics on this platform.")