Always try to delete the data file before and after the test.

This will hopefully avoid spurious failures if the file doesn't
have the proper permissions to write for some reason.

Lib/test/test_gzip.py

@@ -25,13 +25,10 @@ class TestGzip(unittest.TestCase):
     filename = test_support.TESTFN
 
     def setUp (self):
-        pass
+        test_support.unlink(self.filename)
 
     def tearDown (self):
-        try:
-            os.unlink(self.filename)
-        except os.error:
-            pass
+        test_support.unlink(self.filename)
 
 
     def test_write (self):

Lib/test/test_io.py

@@ -79,6 +79,9 @@ class MockNonBlockWriterIO(io.RawIOBase):
 
 class IOTest(unittest.TestCase):
 
+    def setUp(self):
+        test_support.unlink(test_support.TESTFN)
+
     def tearDown(self):
         test_support.unlink(test_support.TESTFN)
 
@@ -619,6 +622,7 @@ class TextIOWrapperTest(unittest.TestCase):
     def setUp(self):
         self.testdata = b"AAA\r\nBBB\rCCC\r\nDDD\nEEE\r\n"
         self.normalized = b"AAA\nBBB\nCCC\nDDD\nEEE\n".decode("ascii")
+        test_support.unlink(test_support.TESTFN)
 
     def tearDown(self):
         test_support.unlink(test_support.TESTFN)