Pin Pecan to 0.6.0 to fix binary secret decrypts
Pin Pecan to 0.6.0 to fix binary secret decrypts

With the latest vesion of Pecan (0.7.0) attempts to GET binary secrets
with an Accept header of application/octet-stream result in a
Pecan/WebOb error trying to utf-8 decode the binary response.
See this link for more details:
https://bugs.launchpad.net/pecan/+bug/1373003

Change-Id: Id9469cb836cfc34636859d4cc8c0bce234e64e92
Related-Bug: #1373003

openstack/barbican,cloudkeep/barbican,MCDong/barbican,jmvrbanac/barbican,jmvrbanac/barbican,openstack/barbican,cneill/barbican,cneill/barbican,MCDong/barbican,cloudkeep/barbican