I'm having the same error with Debian jessie. This started occurring after upgrading to:
apt (1.1~exp9) experimental; urgency=medium
A new algorithm for pinning has been implemented, it now assigns a
pin priority to a version instead of assigning a pin to a package.
This might break existing corner cases of pinning, if they use multiple
pins involving the same package name or patterns matching the same
package name, but should overall lead to pinning that actually works
as intended and documented.
-- Julian Andres Klode <
jak@debian.org> Mon, 17 Aug 2015 14:45:17 +0200
W: Failed to fetch
http://swupdate.openvpn.net/apt/dists/jessie/Release No Hash entry in Release file /var/lib/apt/lists/swupdate.openvpn.net_apt_dists_jessie_Release, which is considered strong enough for security purposes
E: Some index files failed to download. They have been ignored, or old ones used instead.
I deleted the /var/lib/apt/lists/swupdate.openvpn.net_apt_dists_jessie_Release file and ran apt-get update and still have the same error.