add hint message on installing xmllint before running scripts

Author: Apache9

dev-support/create-release/release-util.sh

@@ -138,6 +138,8 @@ function get_api_diff_version {
 # Get all branches that begin with 'branch-', the hbase convention for
 # release branches, sort them and then pop off the most recent.
 function get_release_info {
+  init_xmllint
+
   PROJECT="$(read_config "PROJECT" "$PROJECT")"
   export PROJECT
 
@@ -355,6 +357,17 @@ function init_locale {
   export LANG="$locale_value"
 }
 
+# Check whether xmllint is available
+function init_xmllint {
+  if ! [ -x "$(command -v xmllint)"  ]; then
+    log "Error: xmllint is not available, we need to use it for parsing pom.xml." >&2
+    log "Ubuntu: apt install libxml2-utils"
+    log "CentOS: yum install xmlstarlet"
+    log "Mac OS: brew install xmlstarlet"
+    exit 1
+  fi
+}
+
 # Initializes JAVA_VERSION to the version of the JVM in use.
 function init_java {
   if [ -z "$JAVA_HOME" ]; then