Is there a minimum Python requirement to build Python?

Python 3.5 does not build with Python 2.6. Python 3.4, Python 3.3, and Python 2.7 build with Python 2.6 so this is recent change in build requirements.

For example, this build failure occurs on CentOS 6.

python ./Parser/asdl_c.py -h Include ./Parser/Python.asdl
Traceback (most recent call last):
  File "./Parser/asdl_c.py", line 6, in <module>
    import asdl
  File "Parser/asdl.py", line 36
    builtin_types = {'identifier', 'string', 'bytes', 'int', 'object', 'singleton'}
                                 ^
SyntaxError: invalid syntax