Python 3.5 on Wily has a broken (or missing) zlib

[Salim Fadhley]

System installed version of Python has a defective zlib library:

Python 3.5 seems to be missing this module:

sal@gruntyman:~/workspace/ladygeek$ python3.5
Python 3.5.0 (default, Sep 15 2015, 21:54:38)
[GCC 4.9.2] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import zlib
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named 'zlib'
>>>

but Python 2.7 seems to be fine

sal@gruntyman:~/workspace/ladygeek$ python
Python 2.7.10 (default, Oct 14 2015, 16:09:02)
[GCC 5.2.1 20151010] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import zlib
>>>

and so does Python 3.4

sal@gruntyman:~/workspace/ladygeek$ python3.4
Python 3.4.3+ (default, Oct 14 2015, 16:03:50)
[GCC 5.2.1 20151010] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import zlib
>>>

sal@gruntyman:~/workspace/ladygeek$ lsb_release -rd
Description: Ubuntu 15.10
Release: 15.10

[Salim Fadhley (salimfadhley-d)]

Tried a re-install of Python 3.5 components, no change.