*** This bug has been marked as a duplicate of bug 1062655 ***

The upstream fix for this is trivial so I'm proposing it for 2.0.3.  It does look like the code for this in 2.1 will be completely different since we will no longer need the cartridge cache.

Upstream commit

commit a012f7e3e7231ac56759dfbdd6868f8b8781a7b3
Author: Rajat Chopra <rchopra>
Date:   Tue Dec 3 14:19:48 2013 -0800

    fix bz1036507 - improve error message

openshift enterprise: 2014-02-10.2

[root@br215 ~]# rhc app-create testappa https://s3-eu-west-1.amazonaws.com/cpg.openshift.cartridges/bugrepro/diy-cart/manifffest.yml
The cartridge 'https://s3-eu-west-1.amazonaws.com/cpg.openshift.cartridges/bugrepro/diy-cart/manifffest.yml' will be downloaded and installed

Application Options
-------------------
Domain:     nweidomain
Cartridges: https://s3-eu-west-1.amazonaws.com/cpg.openshift.cartridges/bugrepro/diy-cart/manifffest.yml
Gear Size:  default
Scaling:    no

Creating application 'testappa' ... Invalid cartridge, error downloading from url 'https://s3-eu-west-1.amazonaws.com/cpg.openshift.cartridges/bugrepro/diy-cart/manifffest.yml'

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHBA-2014-0209.html