Object_storage failing with "STDOUT: STDERR: Warning: Permanently added '108.170.222.218' (ECDSA) to the list of known hosts. Usage: pip COMMAND [OPTIONS]  pip: error: No command by the name pip show   (maybe you meant "pip install show")"
./pkb.py --image=debian-7 --zones=us-central1-c --machine_type=n1-standard-8 --benchmarks=object_storage_service --storage=GCP --object_storage_scenario=api_data

...
STDOUT: STDERR: Warning: Permanently added '108.170.222.218' (ECDSA) to the list of known hosts. Usage: pip COMMAND [OPTIONS]  pip: error: No command by the name pip show   (maybe you meant "pip install show")"

...

perfkit@pkb-d8f9db39-0:~$ pip --version
pip 1.1 from /usr/lib/python2.7/dist-packages (python 2.7)

To fix the issue I upgraded pip...
$ sudo apt-get remove python-pip
$ wget https://bootstrap.pypa.io/get-pip.py
$ sudo python get-pip.py

It looks like the root issues is Debian-7 images are pulling a really old version of pip.  I suggest we update the package install to wget the latest like above.

diff --git a/perfkitbenchmarker/linux_packages/pip.py b/perfkitbenchmarker/linux_packages/pip.py
index fd824cb1..dfca23a6 100644
--- a/perfkitbenchmarker/linux_packages/pip.py
+++ b/perfkitbenchmarker/linux_packages/pip.py
@@ -25,6 +25,7 @@ from perfkitbenchmarker import vm_util
 def _Install(vm):
   """Install pip on the VM."""
   vm.InstallPackages('python-pip')
+  vm.RemoteCommand('sudo pip install -U pip')  # Make pip upgrade pip
   vm.RemoteCommand('mkdir -p {0} && pip freeze > {0}/requirements.txt'.format(
       vm_util.VM_TMP_DIR))
 
['perfkitbenchmarker/linux_packages/pip.py']