Describe -s a little more generically.

Lib/test/regrtest.py

@@ -23,11 +23,12 @@ If no test names are given, all tests are run.
 
 -v is incompatible with -g and does not compare test output files.
 
--s means to run only a single test and exit.  This is useful when Purifying
-the Python interpreter.  The file /tmp/pynexttest is read to find the next
-test to run.  If this file is missing, the first test_*.py file in testdir or
-on the command line is used.  (actually tempfile.gettempdir() is used instead
-of /tmp).
+-s means to run only a single test and exit.  This is useful when doing memory
+analysis on the Python interpreter (which tend to consume to many resources to
+run the full regression test non-stop).  The file /tmp/pynexttest is read to
+find the next test to run.  If this file is missing, the first test_*.py file
+in testdir or on the command line is used.  (actually tempfile.gettempdir() is
+used instead of /tmp).
 
 """