Open Stack

Hi, 
My devstack had been OK a month ago. But recently it keeps having this VersionConflict  error.  If I manually install the required module version, it will move on but then it will error out at some other module.  I have manually installed and fixed about 8 such modules, still it is not ending.  I guess I have something fundamental that I missed.  Could somebody please help me?  I was reading the pip code, there is some replace_conflicting env, but I don’t know how to set it, maybe it is set in vendor package?

Thanks
    2016-12-06 18:50:28.095 | +inc/python:setup_package:354             ?[m? pip_install -e /opt/stack/horizon
    2016-12-06 18:50:28.881 | +inc/python:pip_install:155               ?[m? sudo -H http_proxy= https_proxy= no_proxy= PIP_FIND_LINKS= SETUPTOOLS_SYS_PATH_TECHNIQUE=rewrite /usr/local/bin/pip2.7 install -c /opt/stack/requirements/upper-constraints.txt --upgrade -e /opt/stack/horizon
    2016-12-06 18:50:29.930 | Ignoring dnspython3: markers 'python_version == "3.4"' don't match your environment
    2016-12-06 18:50:29.931 | Ignoring dnspython3: markers 'python_version == "3.5"' don't match your environment
    2016-12-06 18:50:30.276 | Obtaining file:///opt/stack/horizon
    2016-12-06 18:50:33.097 | Exception:
    2016-12-06 18:50:33.098 | Traceback (most recent call last):
    2016-12-06 18:50:33.098 |   File "/usr/local/lib/python2.7/dist-packages/pip/basecommand.py", line 215, in main
    2016-12-06 18:50:33.098 |     status = self.run(options, args)
    2016-12-06 18:50:33.098 |   File "/usr/local/lib/python2.7/dist-packages/pip/commands/install.py", line 335, in run
    2016-12-06 18:50:33.098 |     wb.build(autobuilding=True)
    2016-12-06 18:50:33.098 |   File "/usr/local/lib/python2.7/dist-packages/pip/wheel.py", line 749, in build
    2016-12-06 18:50:33.098 |     self.requirement_set.prepare_files(self.finder)
    2016-12-06 18:50:33.098 |   File "/usr/local/lib/python2.7/dist-packages/pip/req/req_set.py", line 380, in prepare_files
    2016-12-06 18:50:33.098 |     ignore_dependencies=self.ignore_dependencies))
    2016-12-06 18:50:33.098 |   File "/usr/local/lib/python2.7/dist-packages/pip/req/req_set.py", line 521, in _prepare_file
    2016-12-06 18:50:33.098 |     req_to_install.check_if_exists()
    2016-12-06 18:50:33.098 |   File "/usr/local/lib/python2.7/dist-packages/pip/req/req_install.py", line 1036, in check_if_exists
    2016-12-06 18:50:33.098 |     self.req.name
    2016-12-06 18:50:33.098 |   File "/usr/local/lib/python2.7/dist-packages/pip/_vendor/pkg_resources/__init__.py", line 558, in get_distribution
    2016-12-06 18:50:33.098 |     dist = get_provider(dist)
    2016-12-06 18:50:33.098 |   File "/usr/local/lib/python2.7/dist-packages/pip/_vendor/pkg_resources/__init__.py", line 432, in get_provider
    2016-12-06 18:50:33.098 |     return working_set.find(moduleOrReq) or require(str(moduleOrReq))[0]
    2016-12-06 18:50:33.098 |   File "/usr/local/lib/python2.7/dist-packages/pip/_vendor/pkg_resources/__init__.py", line 968, in require
    2016-12-06 18:50:33.098 |     needed = self.resolve(parse_requirements(requirements))
    2016-12-06 18:50:33.098 |   File "/usr/local/lib/python2.7/dist-packages/pip/_vendor/pkg_resources/__init__.py", line 859, in resolve
    2016-12-06 18:50:33.098 |     raise VersionConflict(dist, req).with_context(dependent_req)
    2016-12-06 18:50:33.098 | ContextualVersionConflict: (python-heatclient 1.5.0 (/usr/local/lib/python2.7/dist-packages), Requirement.parse('python-heatclient>=1.6.1'), set(['horizon']))
    2016-12-06 18:50:33.233 | +inc/python:pip_install:1                 ?[m? exit_trap
    2016-12-06 18:50:33.240 | +./stack.sh:exit_trap:487                 ?[m? local r=2
    2016-12-06 18:50:33.250 | ++./stack.sh:exit_trap:488                 ?[m? jobs -p
    2016-12-06 18:50:33.260 | +./stack.sh:exit_trap:488                 ?[m? jobs=
    2016-12-06 18:50:33.269 | +./stack.sh:exit_trap:491                 ?[m? [[ -n '' ]]
    2016-12-06 18:50:33.278 | +./stack.sh:exit_trap:497                 ?[m? kill_spinner