Install EPEL for rhel6 if not detected

Simple check to see if EPEL repo is enabled for RHEL6 and, if not,
automated install of the repo RPM.

Also adds an additional sanity check which checking for pip.  In the
prior case of EPEL being disabled, a RHEL6 host may not have access to
python-pip.  Although this shouldn't happen, its a good sanity check.

Change-Id: I4e8a4dda9475b75d071534d4eef469198502a048

functions

@@ -1413,6 +1413,10 @@ function get_pip_command() {
     else
         which pip
     fi
+
+    if [ $? -ne 0 ]; then
+        die $LINENO "Unable to find pip; cannot continue"
+    fi
 }
 
 # Path permissions sanity check

stack.sh

@@ -51,13 +51,24 @@ fi
 # Installing Open vSwitch on RHEL6 requires enabling the RDO repo.
 RHEL6_RDO_REPO_RPM=${RHEL6_RDO_REPO_RPM:-"http://rdo.fedorapeople.org/openstack/openstack-grizzly/rdo-release-grizzly-3.noarch.rpm"}
 RHEL6_RDO_REPO_ID=${RHEL6_RDO_REPO_ID:-"openstack-grizzly"}
+# RHEL6 requires EPEL for many Open Stack dependencies
+RHEL6_EPEL_RPM=${RHEL6_EPEL_RPM:-"http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm"}
+
 if [[ is_fedora && $DISTRO =~ (rhel6) ]]; then
+
     if ! yum repolist enabled $RHEL6_RDO_REPO_ID | grep -q $RHEL6_RDO_REPO_ID; then
         echo "RDO repo not detected; installing"
-        yum_install $RHEL6_RDO_REPO_RPM
+        yum_install $RHEL6_RDO_REPO_RPM || \
+            die $LINENO "Error installing RDO repo, cannot continue"
     fi
-fi
 
+    if ! yum repolist enabled epel | grep -q 'epel'; then
+        echo "EPEL not detected; installing"
+        yum_install ${RHEL6_EPEL_RPM} || \
+            die $LINENO "Error installing EPEL repo, cannot continue"
+    fi
+
+fi
 
 # Global Settings
 # ===============