pip install fails for acct_mgr-0.5.0

[ferchimi@…]

Hello I'm trying to install Account Manager plugin for my new installation of trac 1.2.3, but if fails: [root@main01 ~]# pip install https://trac-hacks.org/svn/accountmanagerplugin/tags/acct_mgr-0.5.0 Collecting https://trac-hacks.org/svn/accountmanagerplugin/tags/acct_mgr-0.5.0

Using cached https://trac-hacks.org/svn/accountmanagerplugin/tags/acct_mgr-0.5.0 Cannot unpack file /tmp/pip-unpack-zihXkI/acct_mgr-0.5.0 (downloaded from /tmp/pip-req-build-Pk0f7Z, content-type: text/html; charset=UTF-8); cannot detect archive format

Cannot determine archive format of /tmp/pip-req-build-Pk0f7Z

Any ideas? thanks, Fernando