devpi-server-2.5.2: fix for 2.5.1 regression

We have a devpi-server-2.5.2 out which fixes a python2-related regression of 2.5.1. best, holger 2.5.2 (2015-11-20) ------------------ - recognize "pex" for redirections of user/index/NAME to user/index/+simple/NAME just like we do with pip/setuptools. - fix py2 incompatibility introduced with 2.5.1 where we used a unicode header and pyramid only likes str-headers.