The test function's signature should be

    test(methodname, input, output, *args)

but the output argument was omitted.  This caused all tests to fail,
because the expected output was passed as the initial argument to the
method call.  But because of the way the test works (it compares the
results for a regular string to the results for a UserString instance
with the same value, and it's OK if both raise the same exception) the
test never failed!

I've fixed this, and also cleaned up a few warts in the verbose
output.  Finally, I've made it possible to run the test stand-alone in
verbose mode by passing -v as a command line argument.

Now, the test will report failure related to zfill.  That's not my
fault, that's a legitimate problem: the string_tests.py file contains
a test for the zfill() method (just added) but this method is not
implemented.  The responsible party will surely fix this soon now.