Ansible 2.6 under RHEL2.7 Version conflict with setuptools

$ ansible --version
ERROR! Unexpected Exception, this is probably a bug: (setuptools 0.9.8 (/usr/lib/python2.7/site-packages), Requirement.parse('setuptools>=11.3'))
the full traceback was:

Traceback (most recent call last):
File "/bin/ansible", line 97, in
mycli = getattr(import("ansible.cli.%s" % sub, fromlist=[myclass]), myclass)
File "/usr/lib/python2.7/site-packages/ansible/cli/init.py", line 38, in
from ansible.inventory.manager import InventoryManager
File "/usr/lib/python2.7/site-packages/ansible/inventory/manager.py", line 33, in
from ansible.plugins.loader import inventory_loader
File "/usr/lib/python2.7/site-packages/ansible/plugins/loader.py", line 22, in
from ansible.parsing.utils.yaml import from_yaml
File "/usr/lib/python2.7/site-packages/ansible/parsing/utils/yaml.py", line 17, in
from ansible.parsing.yaml.loader import AnsibleLoader
File "/usr/lib/python2.7/site-packages/ansible/parsing/yaml/loader.py", line 30, in
from ansible.parsing.yaml.constructor import AnsibleConstructor
File "/usr/lib/python2.7/site-packages/ansible/parsing/yaml/constructor.py", line 29, in
from ansible.parsing.vault import VaultLib
File "/usr/lib/python2.7/site-packages/ansible/parsing/vault/init.py", line 45, in
from cryptography.hazmat.backends import default_backend
File "/usr/lib64/python2.7/site-packages/cryptography/hazmat/backends/init.py", line 7, in
import pkg_resources
File "/usr/lib/python2.7/site-packages/pkg_resources.py", line 3011, in
parse_requirements(requires), Environment()
File "/usr/lib/python2.7/site-packages/pkg_resources.py", line 630, in resolve
raise VersionConflict(dist,req) # XXX put more info here
VersionConflict: (setuptools 0.9.8 (/usr/lib/python2.7/site-packages), Requirement.parse('setuptools>=11.3'))

How to fix this ?