Ovs vapp stacking Fails when stacked using Master branch and stable/liberty.

Exception:
 Traceback (most recent call last):
   File "/usr/local/lib/python2.7/dist-packages/pip/basecommand.py", line 211, in main
     status = self.run(options, args)
   File "/usr/local/lib/python2.7/dist-packages/pip/commands/install.py", line 305, in run
     wb.build(autobuilding=True)
   File "/usr/local/lib/python2.7/dist-packages/pip/wheel.py", line 705, in build
     self.requirement_set.prepare_files(self.finder)
   File "/usr/local/lib/python2.7/dist-packages/pip/req/req_set.py", line 334, in prepare_files
     functools.partial(self._prepare_file, finder))
   File "/usr/local/lib/python2.7/dist-packages/pip/req/req_set.py", line 321, in _walk_req_to_install
     more_reqs = handler(req_to_install)
  File "/usr/local/lib/python2.7/dist-packages/pip/req/req_set.py", line 505, in _prepare_file
    abstract_dist.prep_for_dist()
  File "/usr/local/lib/python2.7/dist-packages/pip/req/req_set.py", line 123, in prep_for_dist
    self.req_to_install.run_egg_info()
  File "/usr/local/lib/python2.7/dist-packages/pip/req/req_install.py", line 376, in run_egg_info
    self.setup_py, self.name,
   File "/usr/local/lib/python2.7/dist-packages/pip/req/req_install.py", line 347, in setup_py
     import setuptools # noqa
   File "/usr/local/lib/python2.7/dist-packages/setuptools/__init__.py", line 12, in <module>
     from setuptools.extension import Extension
   File "/usr/local/lib/python2.7/dist-packages/setuptools/extension.py", line 8, in <module>
     from .dist import _get_unpatched
   File "/usr/local/lib/python2.7/dist-packages/setuptools/dist.py", line 19, in <module>
     import pkg_resources
   File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 3138, in <module>
     @_call_aside
   File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 3124, in _call_aside
     f(*args, **kwargs)
   File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 3151, in _initialize_master_working_set
     working_set = WorkingSet._build_master()
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 652, in _build_master
    ws = cls()
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 645, in __init__
    self.add_entry(entry)
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 701, in add_entry
    for dist in find_distributions(entry, True):
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2139, in find_on_path
    path_item, entry, metadata, precedence=DEVELOP_DIST
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2521, in from_location
    py_version=py_version, platform=platform, **kw
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2835, in _reload_version
    md_version = _version_from_file(self._get_metadata(self.PKG_INFO))
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2486, in _version_from_file
    line = next(iter(version_lines), '')
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2654, in _get_metadata
    for line in self.get_metadata_lines(name):
  File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2030, in get_metadata_lines
    return yield_lines(self.get_metadata(name))
   File "/usr/local/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2024, in get_metadata
     with io.open(self.path, 'rU', encoding='utf-8') as f:
 IOError: [Errno 2] No such file or directory: '/usr/lib/python2.7/dist-packages/unittest2-0.5.1.egg-info'