Bug report

A clear and concise description of what the bug is.
Include a minimal, reproducible example (https://stackoverflow.com/help/minimal-reproducible-example), if possible.

With following code, f1 is OK, but f2 failed with the error "name 'a' is not defined"

 def f1():
    a = "hello"
    exec("print(a)")
 
 def f2():
    a = "hello"
    exec("def inner(): print(a)\ninner()")
 
 f1()
 f2()

Your environment

• CPython versions tested on:
  Python 3.5.2 (default, Aug 10 2017, 23:51:58)
  [GCC 4.4.3] on linux

• Operating system and architecture:
  Linux 3.10.0-1160.25.1.el7.x86_64