Assign an expression into a single variable. The expression may
    either be an `ast.expr` object or a value to be used as a literal.

def ex_varassign(name, expr):
    """Assign an expression into a single variable. The expression may
    either be an `ast.expr` object or a value to be used as a literal.
    """
    if not isinstance(expr, ast.expr):
        expr = ex_literal(expr)
    return ast.Assign([ex_lvalue(name)], expr)