nal keyword arg "raise_on_error" raises an exception on the
    first unexpected exception or failure. This allows failures to be
    post-mortem debugged.

    Optional keyword arg "parser" specifies a DocTestParser (or
    subclass) that should be used to extract tests from the files.

    Optional keyword arg "encoding" specifies an encoding that should
    be used to convert the file to unicode.

    Advanced tomfoolery:  testmod runs methods of a local instance of
    class doctest.Tester, then merges the results into (or creates)
    global Tester instance doctest.master.  Methods of doctest.master
    can be called directly too, if you want to do something unusual.
    Passing report=0 to testmod is especially useful then, to delay
    displaying a summary.  Invoke doctest.master.summarize(verbose)
    when you're done fiddling.
    ú8Package may only be specified for module-relative paths.rA