`AttributeError：模块'__main__'没有属性'/ home / me /'

Question

在org src中使用unittest

#+begin_src python :session unittest :results output :export none
import unittest

def square(n):
    return n ** 2

class MyCase(unittest.TestCase):
    def test_a(self):
        check = square(3)
        self.assertEqual(check, 9)

unittest.main(exit=False)
#+end_src

#+RESULTS:
: .
: ----------------------------------------------------------------------
: Ran 1 test in 0.000s
:
: OK

在使用ipython时效果很好

#+begin_src ipython :session unittest :results output
import unittest

def square(n):
    return n ** 2

class MyCase(unittest.TestCase):
    def test_a(self):
        check = square(3)
        self.assertEqual(check, 9)

unittest.main(exit=False)
#+end_src

#+RESULTS:
#+begin_example
E
======================================================================
ERROR: /home/me/ (unittest.loader._FailedTest)
----------------------------------------------------------------------
AttributeError: module '__main__' has no attribute '/home/me/'

----------------------------------------------------------------------
Ran 1 test in 0.001s

FAILED (errors=1)
#+end_example

AttributeError: module '__main__' has no attribute '/home/me/'没有提供任何线索。

事物在ipython shell中正常工作

In [30]: %paste         
import unittest

def square(n):
    return n ** 2

class MyCase(unittest.TestCase):
    def test_a(self):
        check = square(3)
        self.assertEqual(check, 9)

unittest.main(exit=False)
## -- End pasted text --
.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK
Out[30]: <unittest.main.TestProgram at 0x7f45b55119d0>

可能是什么问题？