Add directions for when trouble strikes in fetch-skps.

Change-Id: I53c02c12a327f6484f4e45777c0168065adfae75
Reviewed-on: https://skia-review.googlesource.com/91080
Reviewed-by: Ravi Mistry <rmistry@google.com>
Commit-Queue: Herb Derby <herb@google.com>
diff --git a/bin/fetch-skps b/bin/fetch-skps
index 19f46e3..e576859 100755
--- a/bin/fetch-skps
+++ b/bin/fetch-skps
@@ -1,6 +1,8 @@
 #!/bin/sh
 
 # Copies the latest bot-generated SKP set to ./skps.
+# If you are having trouble, please refer to the instructions at:
+# https://sites.google.com/a/google.com/skia/key-resources/skps
 
 set -x
 set -e