Description of problem:
You need to test with old kernel which does not support syscall getentropy
and with rawhide user space. You can use either mock or docker with privileged fedora rawhide container

Version-Release number of selected component (if applicable):
sh# rpm -q python35 glibc
python35-3.5.2-5.fc26.x86_64
glibc-2.24.90-26.fc26.x86_64

sh# uname -a
Linux a38d216e5b76 3.10.0-534.el7.x86_64 #1 SMP Fri Dec 16 08:30:57 EST 2016 x86_64 x86_64 x86_64 GNU/Linux

How reproducible:
Deterministic

Steps to Reproduce:
1. Boot a RHEL-7 system.

2. Install EPEL-7 repositories:
# yum install -y https://dl.fedoraproject.org/pub/epel/7/x86_64/e/epel-release-7-8.noarch.rpm

3. Install mock:
# yum install -y mock

4. Setup a user for running mock
# useradd -G mock mockuser
# su - mockuser

5. Install python3 into a Fedora Rawhide mock root:
$ mock -r fedora-rawhide-x86_64 --install python35

6. Attempt to start python3:
$ mock -r fedora-rawhide-x86_64 --shell python35

Actual results:
sh# python3.5
Fatal Python error: getentropy() failed
Aborted (core dumped)

Expected results:
#python shell is started
Python 3.5.2 (default, Jan  1 2017, 14:15:22) 
[GCC 6.3.1 20161221 (Red Hat 6.3.1-1)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

Additional info:
Workaround is to set env PYTHONHASHSEED
sh# PYTHONHASHSEED=1234 python3.5
Python 3.5.2 (default, Jan  1 2017, 14:15:22) 
[GCC 6.3.1 20161221 (Red Hat 6.3.1-1)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>