Change test_mmap.py to use test_support.TESTFN instead of hardcoded "foo",

and wrap the body in try/finally to ensure TESTFN gets cleaned up no
matter what.

Lib/test/test_mmap.py

-from test_support import verify
+from test_support import verify, TESTFN, unlink
 import mmap
 import os, re, sys
 
@@ -7,9 +7,10 @@ PAGESIZE = mmap.PAGESIZE
 def test_both():
     "Test mmap module on Unix systems and Windows"
 
-    # Create an mmap'ed file
-    f = open('foo', 'w+')
+    # Create a file to be mmap'ed.
+    f = open(TESTFN, 'w+')
 
+    try:    # unlink TESTFN no matter what
         # Write 2 pages worth of data to the file
         f.write('\0'* PAGESIZE)
         f.write('foo')
@@ -118,7 +119,17 @@ def test_both():
                 verify(0, 'Could seek beyond the new size')
 
         m.close()
-    os.unlink("foo")
+
+    finally:
+        try:
+            f.close()
+        except OSError:
+            pass
+        try:
+            unlink(TESTFN)
+        except OSError:
+            pass
+
     print ' Test passed'
 
 test_both()