Pass optional arguments (globals(), locals(), []) to __import__() so
it will run as package test, e.g. this will run the test suite:

    import test.regrtest
    test.regrtest.main()
diff --git a/Lib/test/regrtest.py b/Lib/test/regrtest.py
index ce5e22d..7e1003c 100755
--- a/Lib/test/regrtest.py
+++ b/Lib/test/regrtest.py
@@ -133,7 +133,7 @@
 	    if cfp:
 		sys.stdout = cfp
 		print test		# Output file starts with test name
-	    __import__(test)
+	    __import__(test, globals(), locals(), [])
 	finally:
 	    sys.stdout = save_stdout
     except ImportError, msg: