(this error also occurs with "print_function")

Python 3.1 (r31:73574, Jun 26 2009, 20:21:35) [MSC v.1500 32 bit
(Intel)] on win
32
Type "help", "copyright", "credits" or "license" for more information.
>>> from __future__ import unicode_literals
>>> import doctest
>>> def func1():
...    '''
...    >>> func1()
...    hello
...    '''
...    print('hello')
...
>>> doctest.testmod()
**********************************************************************
File "__main__", line 3, in __main__.func1
Failed example:
    func1()
Exception raised:
    Traceback (most recent call last):
      File "c:\Python31\lib\doctest.py", line 1242, in __run
        compileflags, 1), test.globs)
    ValueError: compile(): unrecognised flags
**********************************************************************
1 items had failures:
   1 of   1 in __main__.func1
***Test Failed*** 1 failures.
TestResults(failed=1, attempted=1)

It seems that "compile" does not recognize some flags:

Python 3.1 (r31:73574, Jun 26 2009, 20:21:35) [MSC v.1500 32 bit
(Intel)] on win
32
Type "help", "copyright", "credits" or "license" for more information.
>>> import __future__
>>> compile('a=5', '<string>', 'single',
__future__.print_function.compiler_flag
)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: compile(): unrecognised flags

here is a monkey patch to work around the problem:

import __future__
import doctest
if sys.version_info.major > 2:
        _extract_future_flags_old = doctest._extract_future_flags
        def _extract_future_flags(globs):
                flags = _extract_future_flags_old(globs)
                flags = flags & ~__future__.division.compiler_flag
                flags = flags & ~__future__.absolute_import.compiler_
                flags = flags & ~__future__.nested_scopes.compiler_fl
                flags = flags & ~__future__.print_function.compiler_f
                flags = flags & ~__future__.unicode_literals.compiler
                flags = flags & ~__future__.with_statement.compiler_f
                return flags
        doctest._extract_future_flags = _extract_future_flags

Fixed in r73782 and r73783.