Failure in bulding flask app

Downloading https://files.pythonhosted.org/packages/6f/e9/08fd439384b7e3d613e75a6c8236b8e64d90c47d23413493b38d4229a9a5/enum34-1.1.2.tar.gz (46kB)
100% |████████████████████████████████| 51kB 11.8MB/s
Complete output from command python setup.py egg_info:
Traceback (most recent call last):
File “”, line 1, in
File “/home/circleci/repo/venv/lib/python3.6/site-packages/setuptools/init.py”, line 5, in
import distutils.core
File “/usr/local/lib/python3.6/distutils/core.py”, line 16, in
from distutils.dist import Distribution
File “/usr/local/lib/python3.6/distutils/dist.py”, line 9, in
import re
File “/usr/local/lib/python3.6/re.py”, line 142, in
class RegexFlag(enum.IntFlag):
AttributeError: module ‘enum’ has no attribute ‘IntFlag’

----------------------------------------

Command “python setup.py egg_info” failed with error code 1 in /tmp/pip-build-klihxmfc/enum34/
You are using pip version 9.0.1, however version 18.1 is available.
You should consider upgrading via the ‘pip install --upgrade pip’ command.
Exited with code 1

The build is here - https://circleci.com/gh/samiujan/sw.practice.essentials/2#tests/containers/0 (I am not sure if this is public)