Helo all,
I successfully followed buildout installation instructions for two third party (collective.twitter and Products.Carousel 2.2.1) products, but neither one appears in Site Setup/Available add-ons. Phone, etc. version info is below, any help is greatly appreciated
Plone 4.1.5 (4114)
CMF 2.2.6
Zope 2.13.13
Python 2.6.6 (r266:84292, Jan 22 2014, 09:42:36) [GCC 4.4.7 20120313 (Red Hat 4.4.7-4)]
PIL 1.1.6
could you please describe exactly what you did?
Did you restart the plone clients after you ran buildout to install them?
Ran buildout a few times with both packages added, last response is below:
[root@gibbon-copy web]# ./bin/buildout
lxml: Static build requested.
Unused options for buildout: 'iavi-parts' 'nginx-parts' 'varnish-supervisor' 'memcached-parts' 'cctg-parts' 'leadtheway-parts' 'nginx-supervisor' 'varnish-parts' 'haproxy-supervisor' 'avrc-parts' 'cnics-parts' 'ari-parts' 'avrctrials-parts' 'haproxy-parts' 'memcached-supervisor'.
Updating pcre-build.
Updating varnish-build.
Updating pcre-source.
Updating nginx-build.
Updating memcached-libevent.
Updating memcached-build.
Updating _mr.developer.
Updating supervisor.
Updating lxml.
lxml: Using existing /usr/local/web/var/cache/eggs/lxml-2.3.1-py2.6-linux-x86_64.egg. Delete it if that one isn't statically compiled.
Updating pylxml.
Updating openldap.
Updating python-ldap.
Updating ldap-conf.
Updating zodbpack.
Updating cfar.
Updating avrc.
Updating zodbpack-config.
Installing instance1.
Couldn't find index page for 'ari.policy' (maybe misspelled?)
Getting distribution for 'ari.policy'.
While:
Installing instance1.
Getting distribution for 'ari.policy'.
Error: Couldn't find a distribution for 'ari.policy'.
*************** PICKED VERSIONS ****************
[versions]
Products.Carousel = 2.2.1
Products.PloneHotfix20110928 = 1.1
Products.PloneHotfix20121106 = 1.0
collective.twitter.portlets = 1.0b5
psycopg2 = 2.4.5
*************** /PICKED VERSIONS ***************
Yes, restarted Plone, postgres and nginx. Even tried rebooting since this is a test server VM.
Should this error message be ignored?
Getting distribution for 'ari.policy'.
Error: Couldn't find a distribution for 'ari.policy'.
Are you sure collective.twitter.portlets and Products.Carousel are among your instance eggs (grep for them in bin/instance)?
Edited the instance file, restarted Plone and that did it, thanks Alessandro!
I am glad I have been helpful 
By the way, you mean you fixed the buildout cfg file and not the bin/instance, don't you?
Must admit that at this point I only fixed the instance file
At least we found out that a misconfigured buildout is the culprit 
Tip: ./bin/buildout annotate may give you some hints about what is happening
your buildout fails because ari.policy can not be found.
If this is your own product, you probably have to add
develop = src/ari.policy
to your buildout.
or remove it from eggs (or remove some other product the requires it)
Thanks again