distro: gnutls: Use the GnuPG mirrors.

* gnu/packages/gnutls.scm (gnutls): Use the gnutls.org/GnuPG URL.

gnu/packages/gnutls.scm

@@ -54,13 +54,13 @@ portable, and only require an ANSI C89 platform.")
   (package
     (name "gnutls")
     (version "3.1.6")
-    (source
-     (origin
+    (source (origin
              (method url-fetch)
-      (uri (string-append
-            "mirror://gnu/gnutls/gnutls-"
-            version
-            ".tar.xz"))
+             (uri
+              ;; Note: Releases are no longer on ftp.gnu.org since the
+              ;; schism (after version 3.1.5).
+              (string-append "mirror://gnupg/gnutls/v3.1/gnutls-"
+                             version ".tar.xz"))
              (sha256
               (base32
                "0zsybr9plllk1phh83bx9bg7c5ccik427j4n3k1s9fiy4j69n0w3"))))