Change minimize-manual to read package section from version

Change minimize-manual to read package section from version instead of
package objects, fixing compatibility with (python-)apt 1.9.0.

debian/changelog

@@ -1,3 +1,10 @@
+livecd-rootfs (2.598) UNRELEASED; urgency=medium
+
+  * Change minimize-manual to read package section from version instead
+    of package objects, fixing compatibility with (python-)apt 1.9.0
+
+ -- Julian Andres Klode <juliank@ubuntu.com>  Mon, 24 Jun 2019 17:53:39 +0200
+
 livecd-rootfs (2.597) eoan; urgency=medium
 
   * Install s390-tools-zkey into the installer layer for zkey support in

minimize-manual

@@ -11,10 +11,11 @@ import apt
 
 def is_root(pkg):
     """Check if the package is a root package (manually inst. meta)"""
+    section = pkg.candidate.section if pkg.candidate else ""
     return (pkg.is_installed and
             not pkg.is_auto_installed and
-            (pkg.section == "metapackages" or
-             pkg.section.endswith("/metapackages")))
+            (section == "metapackages" or
+             section.endswith("/metapackages")))
 
 
 def main():