add __file__ to the globals available for tests loaded via DocFileSuite;
this is useful for locating supporting data files, just as it is in Python
modules
diff --git a/Lib/test/test_doctest.py b/Lib/test/test_doctest.py
index 0ae6b8d..fe4d863 100644
--- a/Lib/test/test_doctest.py
+++ b/Lib/test/test_doctest.py
@@ -2010,6 +2010,14 @@
        modified the test globals.  The test globals are
        automatically cleared for us after a test.
 
+       Tests in a file run using `DocFileSuite` can also access the
+       `__file__` global, which is set to the name of the file
+       containing the tests:
+
+         >>> suite = doctest.DocFileSuite('test_doctest3.txt')
+         >>> suite.run(unittest.TestResult())
+         <unittest.TestResult run=1 errors=0 failures=0>
+
        """
 
 def test_trailing_space_in_test():
diff --git a/Lib/test/test_doctest3.txt b/Lib/test/test_doctest3.txt
new file mode 100644
index 0000000..54a96d5
--- /dev/null
+++ b/Lib/test/test_doctest3.txt
@@ -0,0 +1,5 @@
+
+Here we check that `__file__` is provided:
+
+  >>> type(__file__)
+  <type 'str'>