[SPARK-2118] spark class should complaing if tools jar is missing.

Author: ScrapCodes

bin/spark-class

@@ -130,6 +130,13 @@ else
 fi
 
 if [[ "$1" =~ org.apache.spark.tools.* ]]; then
+  if test -z "$SPARK_TOOLS_JAR"; then
+      cat <<EOF 1>&2
+Failed to find Spark Tools Jar in $FWDIR/tools/target/scala-$SCALA_VERSION/
+You need to build spark before running $1.
+EOF
+      exit 1
+      fi
   CLASSPATH="$CLASSPATH:$SPARK_TOOLS_JAR"
 fi