Fix pycparser installation with older setuptools

pycparser version 2.19 has trouble with older versions of setuptools,
see [1]. This is only an issue in queens and older releases.

[1] - pypa/pip#4104

Change-Id: I2a2b707996e86651aa0289636c187208b4b46b33

run_tests.sh

@@ -238,6 +238,8 @@ fi
 
 # Setup packstack
 if [ "${INSTALL_FROM_SOURCE}" = true ]; then
+  # pycparser 2.19 seems to have trouble with older setuptools versions
+  $SUDO pip install pycparser==2.18
   $SUDO pip install .
   export GEM_BIN_DIR=/tmp/packstackgems/bin/
   export PUPPETFILE_DIR=/usr/share/openstack-puppet/modules