This can actually be reproduced with Python 2.7 too (thanks @thiell to let me know). At first I thought that it was not because it doesn't repro with the stock macOS-shipped Python 2.7.10 on macOS Sierra 10.12.6, where the select.poll() is not available at all, see below.

Updated list of version where I was able to reproduce the error:
- macOS Sierra 10.12.6 with those Python versions: 2.7.10, 2.7.13, 3.3.6, 3.4.6, 3.5.3, 3.6.2, 3.7.0a0 (heads/master:2ef37607b7)
- FreeBSD 11.1 with those Python versions: 2.7.13, 3.7.0a0 (heads/master:2ef37607b7)

For reference, the repro code executed with the stock macOS-shipped Python:
#------
$ /usr/bin/python
Python 2.7.10 (default, Feb  7 2017, 00:08:15)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.34)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import select
>>> p = select.poll()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'module' object has no attribute 'poll'
#------

If the PR 3277 that I've sent against the master branch with the fix will be accepted, I'm ready to send additional PRs to backport the fix in all affected versions.