$ wget "http://winswitch.org/dists/gentoo/xpra-0.0.7.17.ebuild"
--2011-01-24 20:47:30--  http://winswitch.org/dists/gentoo/xpra-0.0.7.17.ebuild
Resolving winswitch.org... 194.145.197.105
Connecting to winswitch.org|194.145.197.105|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 566 [text/plain]
Saving to: `xpra-0.0.7.17.ebuild'

100%[======================================>] 566         --.-K/s   in 0s

2011-01-24 20:47:30 (21.6 MB/s) - `xpra-0.0.7.17.ebuild' saved [566/566]

$ ls /usr/local/portage/net-misc/xpra/
Manifest  xpra-0.0.7.16.ebuild
$ sudo cp xpra-0.0.7.17.ebuild /usr/local/portage/net-misc/xpra/
Password:
$ sudo rm -i /usr/local/portage/net-misc/xpra/*16*
rm: remove regular file `/usr/local/portage/net-misc/xpra/xpra-0.0.7.16.ebuild'? y
$ sudo ebuild /usr/local/portage/net-misc/xpra/*ebuild manifest
>>> Downloading 'http://gentoo.virginmedia.com/distfiles/xpra-0.0.7.17.tar.bz2'
--2011-01-24 20:51:46--  http://gentoo.virginmedia.com/distfiles/xpra-0.0.7.17.tar.bz2
Resolving gentoo.virginmedia.com... 194.117.143.69, 194.117.143.70, 194.117.143.71, ...
Connecting to gentoo.virginmedia.com|194.117.143.69|:80... connected.
HTTP request sent, awaiting response... 404 Not Found
2011-01-24 20:51:46 ERROR 404: Not Found.

...
>>> Downloading 'http://windowswitch.org/src/xpra-0.0.7.17.tar.bz2'
--2011-01-24 20:51:47--  http://windowswitch.org/src/xpra-0.0.7.17.tar.bz2
Resolving windowswitch.org... 194.145.197.105
Connecting to windowswitch.org|194.145.197.105|:80... connected.
HTTP request sent, awaiting response... 301 Moved Permanently
Location: http://winswitch.org//src/xpra-0.0.7.17.tar.bz2 [following]
--2011-01-24 20:51:47--  http://winswitch.org//src/xpra-0.0.7.17.tar.bz2
Resolving winswitch.org... 194.145.197.105
Reusing existing connection to windowswitch.org:80.
HTTP request sent, awaiting response... 200 OK
Length: 887754 (867K) [application/x-bzip2]
Saving to: `/usr/portage/distfiles/xpra-0.0.7.17.tar.bz2'

100%[======================================>] 887,754      251K/s   in 3.5s

2011-01-24 20:51:51 (250 KB/s) - `/usr/portage/distfiles/xpra-0.0.7.17.tar.bz2' saved [887754/887754]

>>> Creating Manifest for /usr/local/portage/net-misc/xpra
912 ~ $ sudo emerge -pv xpra

These are the packages that would be merged, in order:

Calculating dependencies... done!

!!! All ebuilds that could satisfy "xpra" have been masked.
!!! One of the following masked packages is required to complete your request:
- net-misc/xpra-0.0.7.17 (masked by: invalid: IUSE contains defaults, but EAPI doesn't allow them)

For more information, see the MASKED PACKAGES section in the emerge
man page or refer to the Gentoo Handbook.

$
$ eix -I portage$ --format '<installedversions:NAMEVERSION>'
sys-apps/portage-2.1.9.25
$

$ sudo emerge xpra
Password:
Calculating dependencies... done!

>>> Verifying ebuild manifests

>>> Emerging (1 of 1) net-misc/xpra-0.0.7.17 from unknown repo
 * xpra-0.0.7.17.tar.bz2 RMD160 SHA1 SHA256 size ;-) ...                 [ ok ]
 * Package:    net-misc/xpra-0.0.7.17
 * USE:  elibc_glibc kernel_linux server ssh userland_GNU x86
>>> Unpacking source...
>>> Unpacking xpra-0.0.7.17.tar.bz2 to /var/tmp/portage/net-misc/xpra-0.0.7.17/work
>>> Source unpacked in /var/tmp/portage/net-misc/xpra-0.0.7.17/work
>>> Compiling source in /var/tmp/portage/net-misc/xpra-0.0.7.17/work/xpra-0.0.7.17 ...
 * Building of net-misc/xpra-0.0.7.17 with CPython 2.6...
python2.6 setup.py build -b build-2.6
Traceback (most recent call last):
  File "setup.py", line 40, in <module>
    from Cython.Distutils import build_ext
ImportError: No module named Cython.Distutils
 * ERROR: net-misc/xpra-0.0.7.17 failed:
 *   Building failed with CPython 2.6 in distutils_building() function
 *
 * Call stack:
 *     ebuild.sh, line   56:  Called src_compile
 *   environment, line 4850:  Called distutils_src_compile
 *   environment, line 1258:  Called python_execute_function 'distutils_building'
 *   environment, line 3466:  Called die
 * The specific snippet of code:
 *                       die "${failure_message}";
 *
 * If you need support, post the output of 'emerge --info =net-misc/xpra-0.0.7.17',
 * the complete build log and the output of 'emerge -pqv =net-misc/xpra-0.0.7.17'.
 * This ebuild is from an overlay: '/usr/local/portage/'
 * The complete build log is located at '/var/tmp/portage/net-misc/xpra-0.0.7.17/temp/build.log'.
 * The ebuild environment file is located at '/var/tmp/portage/net-misc/xpra-0.0.7.17/temp/environment'.
 * S: '/var/tmp/portage/net-misc/xpra-0.0.7.17/work/xpra-0.0.7.17'

>>> Failed to emerge net-misc/xpra-0.0.7.17, Log file:

>>>  '/var/tmp/portage/net-misc/xpra-0.0.7.17/temp/build.log'
$

Resolved with emerge -1 dev-python/cython-0.13

Not sure if this is a runtime or buildtime-only dep.

When installing xpra using your ebuild, the following ewarn message is given upon completion:

>>> Installing (1 of 1) net-misc/xpra-0.0.7.17-r1
 * Server support requires Xvfb
 * This cannot be pulled in by this ebuild

Surely this dependency should be resolved programatically?