change echo to printf

manage.sh

 
     if [ -z "$1" ]; then
         if [ -z "$VIRTUAL_ENV" ]; then
-            echo "geckodriver can't be installed because VIRTUAL_ENV is not set, you should download it from\n  $GECKODRIVER_URL"
+            printf "geckodriver can't be installed because VIRTUAL_ENV is not set, you should download it from\n  %s" "$GECKODRIVER_URL"
             exit
         else
             GECKODRIVER_DIR="$VIRTUAL_ENV/bin"
         mkdir -p -- "$GECKODRIVER_DIR"
     fi
 
-    echo "Installing $GECKODRIVER_DIR/geckodriver from\n  $GECKODRIVER_URL"
+    printf "Installing %s/geckodriver from\n  %s" "$GECKODRIVER_DIR" "$GECKODRIVER_URL"
 
     FILE="`mktemp`"
     wget -qO "$FILE" -- "$GECKODRIVER_URL" && tar xz -C "$GECKODRIVER_DIR" -f "$FILE" geckodriver