Cleanup yum things

We no longer support platforms with Yum on master.  Cleanup old
references and convert to dnf.

We don't need any of the failure wrapper stuff as dnf runs in strict
mode by default.

There seem to be a few callers out there, so we'll leave it called
yum_install for now.

Change-Id: Ie71a48fd85b00a97a14bf260cd013b18af4cce06

functions-common

@@ -329,9 +329,6 @@ function _ensure_lsb_release {
         sudo zypper -n install lsb-release
     elif [[ -x $(command -v dnf 2>/dev/null) ]]; then
         sudo dnf install -y redhat-lsb-core
-    elif [[ -x $(command -v yum 2>/dev/null) ]]; then
-        # all rh patforms (fedora, centos, rhel) have this pkg
-        sudo yum install -y redhat-lsb-core
     else
         die $LINENO "Unable to find or auto-install lsb_release"
     fi
@@ -1361,7 +1358,7 @@ function uninstall_package {
     if is_ubuntu; then
         apt_get purge "$@"
     elif is_fedora; then
-        sudo ${YUM:-yum} remove -y "$@" ||:
+        sudo dnf remove -y "$@" ||:
     elif is_suse; then
         sudo zypper remove -y "$@" ||:
     else
@@ -1369,8 +1366,11 @@ function uninstall_package {
     fi
 }
 
-# Wrapper for ``yum`` to set proxy environment variables
-# Uses globals ``OFFLINE``, ``*_proxy``, ``YUM``
+# Wrapper for ``dnf`` to set proxy environment variables
+# Uses globals ``OFFLINE``, ``*_proxy``
+# The name is kept for backwards compatability with external
+# callers, despite none of our supported platforms using yum
+# any more.
 # yum_install package [package ...]
 function yum_install {
     local result parse_yum_result
@@ -1378,44 +1378,8 @@ function yum_install {
     [[ "$OFFLINE" = "True" ]] && return
 
     time_start "yum_install"
-
-    # This is a bit tricky, because yum -y assumes missing or failed
-    # packages are OK (see [1]).  We want devstack to stop if we are
-    # installing missing packages.
-    #
-    # Thus we manually match on the output (stack.sh runs in a fixed
-    # locale, so lang shouldn't change).
-    #
-    # If yum returns !0, we echo the result as "YUM_FAILED" and return
-    # that from the awk (we're subverting -e with this trick).
-    # Otherwise we use awk to look for failure strings and return "2"
-    # to indicate a terminal failure.
-    #
-    # [1] https://bugzilla.redhat.com/show_bug.cgi?id=965567
-    parse_yum_result='              \
-        BEGIN { result=0 }          \
-        /^YUM_FAILED/ { result=$2 } \
-        /^No package/ { result=2 }  \
-        /^Failed:/    { result=2 }  \
-        //{ print }                 \
-        END { exit result }'
-    (sudo_with_proxies "${YUM:-yum}" install -y "$@" 2>&1 || echo YUM_FAILED $?) \
-        | awk "$parse_yum_result" && result=$? || result=$?
-
+    sudo_with_proxies dnf install -y "$@"
     time_stop "yum_install"
-
-    # if we return 1, then the wrapper functions will run an update
-    # and try installing the package again as a defense against bad
-    # mirrors.  This can hide failures, especially when we have
-    # packages that are in the "Failed:" section because their rpm
-    # install scripts failed to run correctly (in this case, the
-    # package looks installed, so when the retry happens we just think
-    # the package is OK, and incorrectly continue on).
-    if [ "$result" == 2 ]; then
-        die "Detected fatal package install failure"
-    fi
-
-    return "$result"
 }
 
 # zypper wrapper to set arguments correctly

stack.sh

@@ -283,19 +283,12 @@ fi
 # to pick up required packages.
 
 function _install_epel {
-    # NOTE: We always remove and install latest -- some environments
-    # use snapshot images, and if EPEL version updates they break
-    # unless we update them to latest version.
-    if sudo yum repolist enabled epel | grep -q 'epel'; then
-        uninstall_package epel-release || true
-    fi
-
     # epel-release is in extras repo which is enabled by default
     install_package epel-release
 
     # RDO repos are not tested with epel and may have incompatibilities so
     # let's limit the packages fetched from epel to the ones not in RDO repos.
-    sudo yum-config-manager --save --setopt=includepkgs=debootstrap,dpkg epel
+    sudo dnf config-manager --save --setopt=includepkgs=debootstrap,dpkg epel
 }
 
 function _install_rdo {

stackrc

@@ -813,15 +813,6 @@ SERVICE_GRACEFUL_SHUTDOWN_TIMEOUT=${SERVICE_GRACEFUL_SHUTDOWN_TIMEOUT:-5}
 # Service graceful shutdown timeout
 WORKER_TIMEOUT=${WORKER_TIMEOUT:-90}
 
-# Choose DNF on RedHat/Fedora platforms with it, or otherwise default
-# to YUM.  Can remove this when only dnf is supported (i.e. centos7
-# disappears)
-if [[ -e /usr/bin/dnf ]]; then
-    YUM=${YUM:-dnf}
-else
-    YUM=${YUM:-yum}
-fi
-
 # Common Configuration
 # --------------------