Teach regrtest how to pass on doctest failure msgs. This is done via a horridly inefficient hack in regrtest's Compare class, but it's about as clean as can be: regrtest has to set up the Compare instance before importing a test module, and by the time the module *is* imported it's too late to change that decision. The good news is that the more tests we convert to unittest and doctest, the less the inefficiency here matters. Even now there are few tests with large expected-output files (the new cost here is a Python-level call per .write() when there's an expected- output file).

--- a/Lib/test/test_difflib.py	Sun Sep 09 01:21:31 2001 +0000
+++ b/Lib/test/test_difflib.py	Sun Sep 09 06:12:01 2001 +0000
@@ -1,3 +1,2 @@
-from test_support import verbose
-import doctest, difflib
-doctest.testmod(difflib, verbose=verbose)
+import difflib, test_support
+test_support.run_doctest(difflib)