ENH: Provide message if ParaView is not installed instead of swallowing the error

applications/utilities/postProcessing/graphics/PV3Readers/Allwmake

 #!/bin/sh
 cd ${0%/*} || exit 1    # run from this directory
-set -x
+#set -x
 
 if [ -d "$ParaView_DIR" -a -r "$ParaView_DIR" ]
 then
@@ -15,6 +15,8 @@ then
     wmake libso vtkPV3Readers
     PV3blockMeshReader/Allwmake
     PV3FoamReader/Allwmake
+else
+    echo "ERROR: ParaView not found in $ParaView_DIR"
 fi
 
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