why ?

gistfile1.txt

lucky(~/charms/precise) % cat haproxy/metadata.yaml 
name: haproxy
summary: "fast and reliable load balancing reverse proxy"
maintainer: [Juan Negron <juan@ubuntu.com>, Tom Haddon <tom.haddon@canonical.com>]
description:
 HAProxy is a TCP/HTTP reverse proxy which is particularly suited for high
 availability environments. It features connection persistence through HTTP
 cookies, load balancing, header addition, modification, deletion both ways. It
 has request blocking capabilities and provides interface to display server
 status.
categories: ["cache-proxy"]
requires:
  reverseproxy:
    interface: http
provides:
  website:
    interface: http
  munin:
    interface: munin-node
  nrpe-external-master:
    interface: nrpe-external-master
    scope: container
  local-monitors:
    interface: local-monitors
    scope: container
peers:
  peer:
    interface: haproxy-peer
lucky(~/charms/precise) % juju add-relation w1:website p1:reverseproxy
ERROR service "p1" has no "reverseproxy" relation