[bug] cannot support sympy.init_printing(use_unicode=False)

[Freed-Wu]

In python's repl:

import sympy
sympy.init_printing(use_unicode=False)
sympy.simplify(x ** 2 + 2 * x + 1)

the result is

 2
x  + 2*x + 1

However, in ptpython, it always be

x ** 2 + 2 * x + 1

It seems that sympy.init_printing cannot work in ptpython.

[jonathanslenders]

This is probably due to ptpython not yet using ``sys.displayhook`.