There are many projects asking for new builds recently, but 6591 has been broken since 2016/Dec27.

preflight is broken for few packages lacking of checksum, for example:
https://uberchromegw.corp.google.com/i/chromeos.branch/builders/veyron_pinky%20pre-flight%20factory-veyron-6591.B/builds/371/steps/BuildPackages/logs/stdio

xcb-util-renderutil-0.3.8:   File "/usr/lib64/python2.7/site-packages/_emerge/AsynchronousTask.py", line 175, in _wait_hook
xcb-util-renderutil-0.3.8:     self._exit_listener_stack.pop()(self)
xcb-util-renderutil-0.3.8:   File "/usr/lib64/python2.7/site-packages/_emerge/Binpkg.py", line 270, in _clean_exit
xcb-util-renderutil-0.3.8:     str(portage.checksum.perform_md5(pkg_path)) + "\n"))
xcb-util-renderutil-0.3.8:   File "/usr/lib64/python2.7/site-packages/portage/checksum.py", line 187, in perform_md5
xcb-util-renderutil-0.3.8:     return perform_checksum(x, "MD5", calc_prelink)[0]
xcb-util-renderutil-0.3.8:   File "/usr/lib64/python2.7/site-packages/portage/checksum.py", line 390, in perform_checksum
xcb-util-renderutil-0.3.8:     myhash, mysize = hashfunc_map[hashname](myfilename)
xcb-util-renderutil-0.3.8:   File "/usr/lib64/python2.7/site-packages/portage/checksum.py", line 52, in __call__
xcb-util-renderutil-0.3.8:     with _open_file(filename) as f:
xcb-util-renderutil-0.3.8:   File "/usr/lib64/python2.7/site-packages/portage/checksum.py", line 31, in _open_file
xcb-util-renderutil-0.3.8:     raise portage.exception.FileNotFound(filename)
xcb-util-renderutil-0.3.8: FileNotFound: /build/veyron_pinky/packages/x11-libs/xcb-util-renderutil-0.3.8.tbz2

And in full builder, it failed at some weird stage:
https://uberchromegw.corp.google.com/i/chromeos.branch/builders/veyron_speedy%20factory%20factory-veyron-6591.B/builds/205/steps/BuildPackages/logs/stdio

sgml-common-0.6.3-r5:  * Running automake --add-missing --copy --foreign ...
sgml-common-0.6.3-r5:  [ !! ]
sgml-common-0.6.3-r5: 
sgml-common-0.6.3-r5:  * Failed Running automake !