Comment 17 for bug 245219

Very old bug. I just tried wgetting http://archive.ubuntu.com/ubuntu/dists/disco-proposed/main/dist-upgrader-all/current/disco.tar.gz.gpg with and without a proxy, and it worked just fine, even though it's still being identified as x-gzip:
andreas@nsnx:~/x$ http_proxy=http://squid-ds216.lxd:3128/ wget --no-cache http://archive.ubuntu.com/ubuntu/dists/disco-proposed/main/dist-upgrader-all/current/disco.tar.gz.gpg
--2019-02-06 14:57:16-- http://archive.ubuntu.com/ubuntu/dists/disco-proposed/main/dist-upgrader-all/current/disco.tar.gz.gpg
Resolving squid-ds216.lxd (squid-ds216.lxd)... 10.0.100.206
Connecting to squid-ds216.lxd (squid-ds216.lxd)|10.0.100.206|:3128... connected.
Proxy request sent, awaiting response... 200 OK
Length: 1554 (1,5K) [application/x-gzip]
Saving to: ‘disco.tar.gz.gpg’

disco.tar.gz.gpg 100%[================================================================================================================================>] 1,52K --.-KB/s in 0s

2019-02-06 14:57:17 (75,9 MB/s) - ‘disco.tar.gz.gpg’ saved [1554/1554]

andreas@nsnx:~/x$ file disco.tar.gz.gpg
disco.tar.gz.gpg: PGP signature Signature (old)

andreas@nsnx:~/x$ cat disco.tar.gz.gpg
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1

iQIcBAABCgAGBQJcRf7TAAoJEDtP5qzAsh8yFaMQANW6mTi+bCHp08NeFC7wcSal
z2xtiNxm2FYIJ9BkZZGvS1YI5rQsS8X0x1auU21mCus39anOUp5XaWUDPVMfjuZO
RxajHohB1YUAiLMi7zY86LkpEMSYOMknwhH57ZZSMlHELyqSb/hKzawPfrBKTnWo
N0b0+3hbpwi7tRZu0Y3Y3cooeH6C6lgFJEAPkFXcgdFw72OtGs1ByOIkRlr4AUb7
...

I'm going to mark this bug as incomplete, and it will expire automatically unless someone has something to add.