debian packaging: expand documentation

And print what the linter expects: 4 spaces.

Signed-off-by: Stephan Pleines <pleines.stephan@gmail.com>
Change-Id: Idf4d267457860faacf897f215b782ed8616ec7a7
diff --git a/debian/download_packages.py b/debian/download_packages.py
index 2d284d7..82f01ce 100755
--- a/debian/download_packages.py
+++ b/debian/download_packages.py
@@ -147,7 +147,7 @@
     contents.sort()
     print("_files = {")
     for deb in contents:
-        print('  "%s": "%s",' % (deb, sha256_checksum(deb)))
+        print('    "%s": "%s",' % (deb, sha256_checksum(deb)))
     print("}")