Use AOSP Installer if permission check fails
If the old repo index is used and the permission check fails in ApkVerifier, this allows a fallback to the AOSP DefaultInstaller to show all permissions. This has been discussed in https://gitlab.com/fdroid/fdroidclient/issues/704
Unfortunately, this shows our permission screen before download and then afterwards when the ApkVerifier
fails the permission screen of the AOSP DefaultInstaller, i.e., the user sees two permission screen which she needs to acknowledge. This should only happen if an old repo format is used, thus I think this is okay. I don't know of any other solution to this problem.