'Look for the named local variable, returning a (PyObjectPtr, scope) pair
where scope is a string \'local\', \'global\', \'builtin\'
If not found, return (None, None)'

def get_var_by_name(self, name):

    for (pyop_name, pyop_value) in self.iter_locals():
        if (name == pyop_name.proxyval(set())):
            return (pyop_value, 'local')
    for (pyop_name, pyop_value) in self.iter_globals():
        if (name == pyop_name.proxyval(set())):
            return (pyop_value, 'global')
    for (pyop_name, pyop_value) in self.iter_builtins():
        if (name == pyop_name.proxyval(set())):
            return (pyop_value, 'builtin')
    return (None, None)
