'Return the current working directory path.
Examples
In [9]: pwd
Out[9]: \'/home/tsuser/sprint/ipython\''

@skip_doctest
@line_magic
def pwd(self, parameter_s=''):

    try:
        return os.getcwd()
    except FileNotFoundError:
        raise UsageError('CWD    no    longer    exists    -    please    use    %cd    to    change    directory.')
