Issue #8438: Remove reference to the missing "surrogateescape" encoding

error handler from the new IO library.

Lib/test/test_fileio.py

@@ -12,6 +12,7 @@ from functools import wraps
 
 from test.test_support import TESTFN, check_warnings, run_unittest, make_bad_fd
 from test.test_support import py3k_bytes as bytes
+from test.script_helper import run_python
 
 from _io import FileIO as _FileIO
 
@@ -397,6 +398,25 @@ class OtherFileTests(unittest.TestCase):
             self.assertRaises(ValueError, _FileIO, "/some/invalid/name", "rt")
             self.assertEqual(w.warnings, [])
 
+    def test_surrogates(self):
+        # Issue #8438: try to open a filename containing surrogates.
+        # It should either fail because the file doesn't exist or the filename
+        # can't be represented using the filesystem encoding, but not because
+        # of a LookupError for the error handler "surrogateescape".
+        filename = u'\udc80.txt'
+        try:
+            with _FileIO(filename):
+                pass
+        except (UnicodeEncodeError, IOError):
+            pass
+        # Spawn a separate Python process with a different "file system
+        # default encoding", to exercise this further.
+        env = dict(os.environ)
+        env[b'LC_CTYPE'] = b'C'
+        _, out = run_python('-c', 'import _io; _io.FileIO(%r)' % filename, env=env)
+        if ('UnicodeEncodeError' not in out and
+            'IOError: [Errno 2] No such file or directory' not in out):
+            self.fail('Bad output: %r' % out)
 
 def test_main():
     # Historically, these tests have been sloppy about removing TESTFN.