> Test that your fix does not break the case of 8-bit non-ascii docstring.

Do you mean double escaping of the backslash as in t\xe4st changed to t\\xe4st due to this PR? 

➜  cpython git:(bpo10417) $ cat /tmp/foo.py
# -*- coding: utf-8 -*-
import unittest

class UnicodeTest(unittest.TestCase):
    def test_unicode_docstring(self):
        u"""docstring with unicode character. t\xe4st"""
        self.assertEqual(1+1, 2)

if __name__ == '__main__':
    unittest.main()

# ASCII encoding

➜  cpython git:(bpo10417) $ PYTHONIOENCODING=ascii ./python.exe /tmp/foo.py --verbose
test_unicode_docstring (__main__.UnicodeTest)
docstring with unicode character. t\xe4st ... ok

----------------------------------------------------------------------
Ran 1 test in 0.019s

OK

# utf-8 encoding

➜  cpython git:(bpo10417) $ ./python.exe /tmp/foo.py --verbose
test_unicode_docstring (__main__.UnicodeTest)
docstring with unicode character. täst ... ok

----------------------------------------------------------------------
Ran 1 test in 0.004s

OK