I have the same problem

2015-11-24 14:37:41.619 | pip: 1.5.4
2015-11-24 14:37:41.620 | + uninstall_package python-pip
2015-11-24 14:37:41.620 | + is_ubuntu
2015-11-24 14:37:41.620 | + [[ -z deb ]]
2015-11-24 14:37:41.620 | + '[' deb = deb ']'
2015-11-24 14:37:41.621 | + apt_get purge python-pip
2015-11-24 14:37:41.628 | + sudo DEBIAN_FRONTEND=noninteractive http_proxy= https_proxy= no_proxy= apt-get --option Dpkg::Options::=--force-co$
2015-11-24 14:37:41.654 | Reading package lists...
2015-11-24 14:37:42.179 | Building dependency tree...
2015-11-24 14:37:42.181 | Reading state information...
2015-11-24 14:37:42.745 | The following packages were automatically installed and are no longer required:
2015-11-24 14:37:42.746 |   python-chardet-whl python-colorama python-colorama-whl python-distlib
2015-11-24 14:37:42.746 |   python-distlib-whl python-html5lib python-html5lib-whl python-pip-whl
2015-11-24 14:37:42.746 |   python-requests-whl python-setuptools-whl python-six-whl python-urllib3-whl
2015-11-24 14:37:42.746 |   python-wheel python3-pkg-resources
2015-11-24 14:37:42.746 | Use 'apt-get autoremove' to remove them.
2015-11-24 14:37:42.890 | The following packages will be REMOVED:
2015-11-24 14:37:42.891 |   python-pip*
2015-11-24 14:37:43.191 | 0 upgraded, 0 newly installed, 1 to remove and 4 not upgraded.
2015-11-24 14:37:43.191 | After this operation, 477 kB disk space will be freed.
2015-11-24 14:37:43.274 | (Reading database ... 75233 files and directories currently installed.)
2015-11-24 14:37:43.284 | Removing python-pip (1.5.4-1ubuntu3) ...
2015-11-24 14:37:43.420 | Processing triggers for man-db (2.6.7.1-1ubuntu1) ...
2015-11-24 14:37:44.104 | + install_get_pip
2015-11-24 14:37:44.104 | + [[ ! -r /home/silvia/devstack/files/get-pip.py ]]
2015-11-24 14:37:44.104 | + [[ -r /home/silvia/devstack/files/get-pip.py.downloaded ]]
2015-11-24 14:37:44.105 | + curl --retry 6 --retry-delay 5 -z /home/silvia/devstack/files/get-pip.py -o /home/silvia/devstack/files/get-pip.py$
2015-11-24 14:37:44.121 |   % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
2015-11-24 14:37:44.122 |                                  Dload  Upload   Total   Spent    Left  Speed
2015-11-24 14:37:44.344 | ^M  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0^M  0     0    0     0    0     0   $
2015-11-24 14:37:44.348 | + touch /home/silvia/devstack/files/get-pip.py.downloaded
2015-11-24 14:37:44.352 | + sudo -H -E python /home/silvia/devstack/files/get-pip.py
2015-11-24 14:37:47.082 | Requirement already up-to-date: pip in /usr/local/lib/python2.7/dist-packages
2015-11-24 14:37:47.688 | + [[ -n '' ]]
2015-11-24 14:37:47.688 | + pip_install -U setuptools
2015-11-24 14:37:47.708 | [ERROR] /home/silvia/devstack/inc/python:34 Unable to find pip; cannot continue
2015-11-24 14:37:49.319 | + sudo -H http_proxy= https_proxy= no_proxy= PIP_FIND_LINKS= '[Call' 'Trace]' /home/silvia/devstack/tools/install_pi$
2015-11-24 14:37:49.327 | sudo: [Call: command not found
2015-11-24 14:37:49.329 | ++ err_trap
2015-11-24 14:37:49.329 | ++ local r=1
2015-11-24 14:37:49.329 | stack.sh failed: full log in stack.sh.log.2015-11-24-153704
2015-11-24 14:37:49.332 | Error on exit


Moreover the folder /usr/local/lib/python2.7/site-packages/ is empty and /usr/lib/python2.7/ (as Arun has indicated) does not have site-packages folder.