Returns position of 1st char after assignment traget.

        If there is no assignment, -1 is returned

        If there are more than one of any ( expressions or assigments)
        then a ValueError is raised.

def _get_assignment_target_end(self, ast_module):
        """Returns position of 1st char after assignment traget.

        If there is no assignment, -1 is returned

        If there are more than one of any ( expressions or assigments)
        then a ValueError is raised.

        """

        if len(ast_module.body) > 1:
            raise ValueError("More than one expression or assignment.")

        elif len(ast_module.body) > 0 and \
                type(ast_module.body[0]) is ast.Assign:
            if len(ast_module.body[0].targets) != 1:
                raise ValueError("More than one assignment target.")
            else:
                return len(ast_module.body[0].targets[0].id)

        return -1