changed error message for invalid characters in filename as per #501
changed error message for invalid characters in filename as per #501

EarthSystemCoG/COG,EarthSystemCoG/COG,EarthSystemCoG/COG,sashakames/COG,EarthSystemCoG/COG,sashakames/COG,sashakames/COG,sashakames/COG,EarthSystemCoG/COG,EarthSystemCoG/COG,EarthSystemCoG/COG,sashakames/COG,sashakames/COG,sashakames/COG