'Returns the appropriate print string depending on the
version of Python.
Examples:
* Python 2
.. code-block:: python
>>> self.print_string(\'sys.prefix\')
\'print sys.prefix\'
* Python 3
.. code-block:: python
>>> self.print_string(\'sys.prefix\')
\'print(sys.prefix)\''

def print_string(self, string):

    if self.spec.satisfies('@:2'):
        return 'print    {0}'.format(string)
    else:
        return 'print({0})'.format(string)
