Add rhel 8+ dnf support

Signed-off-by: Corey Hemminger <hemminger@hotmail.com>

Author: Stromweld

libraries/linux_updates.rb

@@ -208,10 +208,17 @@ def packages
   end
 
   def updates
-    rhel_updates = <<~PRINT_JSON
-      #!/bin/sh
-      python -c 'import sys; sys.path.insert(0, "/usr/share/yum-cli"); import cli; ybc = cli.YumBaseCli(); ybc.setCacheDir("/tmp"); list = ybc.returnPkgLists(["updates"]);res = ["{\\"name\\":\\""+x.name+"\\", \\"version\\":\\""+x.version+"-"+x.release+"\\",\\"arch\\":\\""+x.arch+"\\",\\"repository\\":\\""+x.repo.id+"\\"}" for x in list.updates]; print "{\\"available\\":["+",".join(res)+"]}"'
-    PRINT_JSON
+    rhel_updates = if os.release.to_i > 7
+                     <<~PRINT_JSON
+                       #!/usr/bin/sh
+                       /usr/libexec/platform-python -c 'import dnf; base = dnf.Base(); base.read_all_repos(); base.fill_sack(); q = base.sack.query(); list = list(q.upgrades()); res = ["{\\"name\\":\\""+x.name+"\\",\\"version\\":\\""+x.version+"-"+x.release+"\\",\\"arch\\":\\""+x.arch+"\\",\\"repository\\":\\""+x.reponame+"\\"}" for x in list]; print("{\\"available\\":["+",".join(res)+"]}")'
+                     PRINT_JSON
+                   else
+                     <<~PRINT_JSON
+                       #!/bin/sh
+                       python -c 'import sys; sys.path.insert(0, "/usr/share/yum-cli"); import cli; ybc = cli.YumBaseCli(); ybc.setCacheDir("/tmp"); list = ybc.returnPkgLists(["updates"]);res = ["{\\"name\\":\\""+x.name+"\\", \\"version\\":\\""+x.version+"-"+x.release+"\\",\\"arch\\":\\""+x.arch+"\\",\\"repository\\":\\""+x.repo.id+"\\"}" for x in list.updates]; print "{\\"available\\":["+",".join(res)+"]}"'
+                     PRINT_JSON
+                   end
     cmd = @inspec.bash(rhel_updates)
     unless cmd.exit_status.zero?
       # essentially we want https://github.com/chef/inspec/issues/1205