This is not necessarily a failure.
When executing sudo apt install [package], apt drops privileges to the _apt user while downloading the file, usually from a remote mirror.
As apt is being told to download a package within file:///home/user/…, it is unable to access as /home/user blocks all permissions except owner. It is non-fatal and only a warning.
apt is informing that it didn’t drop privileges to retrieve the file, which is typically good security practice (apt doesn’t need to be root to download a file, but it does need to be root to install it). If the package file is in a directory accessible by the user _apt, the message will go away.