On my Linux Mint 19.1:
```bash
$ umask
0022
```

After the first run of `bitcoin-qt -sysperm=false` the `0700` permissions are expected for both the datadir (`~/.bitcoin`) and the walletdir (`~/.bitcoin/wallets`).

Actually, the directories are created with such access permissions:
```bash
$ stat ~/.bitcoin | grep Uid
Access: (0755/drwxr-xr-x)  Uid: ( 1000/ hebasto)   Gid: ( 1000/ hebasto)
$ stat ~/.bitcoin/wallets | grep Uid
Access: (0755/drwxr-xr-x)  Uid: ( 1000/ hebasto)   Gid: ( 1000/ hebasto)
```

Refs:
- #4286
- #13371
- #13389

NOTE: reading through the initial PR #4286 makes me think it was controversial. Is it a better and simpler way to just get rid of `-sysperm` option? I believe a user who needs this option can easily run `chown` command.
assert(IsReachable(net));
            if (!nets.count(net))
                SetReachable(net, false);
        }
    }
    if (!args.IsArgSet("-cjdnsreachable")) {
        if (args.IsArgSet("-onlynet") && IsReachable(NET_CJDNS)) {
            return InitError(
                _("Outbound connections restricted to CJDNS (-onlynet=cjdns) but "
                  "-cjdnsreachable is not provided"));
        }
        SetReachable(NET_CJDNS, false);
    }
     
     
     
     
     
     
     
    if (args.GetBoolArg("-dnsseed") == true && !IsReachable(NET_IPV4) && !IsReachable(NET_IPV6)) {
        return InitError(strprintf(_("Incompatible options: -dnsseed=1 was explicitly specified, but -onlynet forbids connections to IPv4IPv6")));
    };
     
    fNameLookup = args.GetBoolArg("-dns", DEFAULT_NAME_LOOKUP);
    Proxy onion_proxy;
    bool proxyRandomize = args.GetBoolArg("-proxyrandomize", DEFAULT_PROXYRANDOMIZE);