make python untar command into a scrollable pre section.

Author: rouilj

website/www/index.txt

@@ -182,8 +182,9 @@ Follow the source gratification mode with these steps (change the
 1. ``python3 -m pip download roundup``
 2. ``tar -xzvf roundup-2.3.0.tar.gz``
 
-   * if you don't have a tar command (e.g windows), use:
-     ``python -c "import tarfile, sys; tarfile.open(sys.argv[1]).extractall();" roundup-2.3.0.tar.gz``
+   * if you don't have a tar command (e.g windows), use::
+
+       python -c "import tarfile, sys; tarfile.open(sys.argv[1]).extractall();" roundup-2.3.0.tar.gz
 
 
 3. ``cd roundup-2.3.0``