add doc link

Author: gengliangwang

bin/load-spark-env.sh

@@ -49,9 +49,11 @@ if [ -z "$SPARK_SCALA_VERSION" ]; then
 
   ASSEMBLY_DIR_1="${SPARK_HOME}/assembly/target/scala-${SCALA_VERSION_1}"
   ASSEMBLY_DIR_2="${SPARK_HOME}/assembly/target/scala-${SCALA_VERSION_2}"
+  ENV_VARIABLE_DOC="https://spark.apache.org/docs/latest/configuration.html#environment-variables"
   if [[ -d "$ASSEMBLY_DIR_1" && -d "$ASSEMBLY_DIR_2" ]]; then
     echo "Presence of build for multiple Scala versions detected ($ASSEMBLY_DIR_1 and $ASSEMBLY_DIR_2)." 1>&2
     echo "Remove one of them or, export SPARK_SCALA_VERSION=$SCALA_VERSION_1 in ${SPARK_ENV_SH}." 1>&2
+    echo "Visit ${ENV_VARIABLE_DOC} for more details about setting environment variables in spark-env.sh." 1>&2
     exit 1
   fi