Improve error message passing a URL with scheme to rehost.sh

Change-Id: I77cdd9f075f118ec2f917712832e55307f8055d1
Signed-off-by: Brian Silverman <bsilver16384@gmail.com>
diff --git a/tools/rehost.sh b/tools/rehost.sh
index 86ca488..3031aba 100755
--- a/tools/rehost.sh
+++ b/tools/rehost.sh
@@ -7,6 +7,11 @@
 
 readonly LOCALPATH="$(basename "${1}")"
 
+if echo "${1}" | grep --quiet http; then
+  echo "Argument must not include the scheme (remove the https://)" >&2
+  exit 1
+fi
+
 set -e
 curl -L "https://${1}" -o "${LOCALPATH}"