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/Doc/lib/libdoctest.tex b/Doc/lib/libdoctest.tex
index b982a73..0f32f7d 100644
--- a/Doc/lib/libdoctest.tex
+++ b/Doc/lib/libdoctest.tex
@@ -1107,6 +1107,10 @@
   defaults to a normal parser (i.e., \code{\class{DocTestParser}()}).
 
   \versionadded{2.4}
+
+  Starting in Python 2.5, the global \code{__file__} was added to the
+  globals provided to doctests loaded from a text file using
+  \function{DocFileSuite()}.
 \end{funcdesc}
 
 \begin{funcdesc}{DocTestSuite}{\optional{module}\optional{,