Fix command-line execution for listing packages.

Author: mtwebster

usr/lib/linuxmint/mintinstall/mintinstall.py

@@ -2124,8 +2124,9 @@ def export_listing(self, flatpak_only=False):
 
         from mintcommon.installer import cache
 
-        self.installer.cache = cache.PkgCache(self.installer.have_flatpak)
-        self.installer.force_new_cache()
+        self.installer.cache = cache.PkgCache(None, None, self.installer.have_flatpak)
+        self.installer.cache._generate_cache_thread()
+
         self.installer.backend_table = {}
 
         self.installer.initialize_appstream()