I believe I know what the issue is here. We have a fix awaiting release, but you may be able to work around it in the meantime by uninstalling the python “requests” package on your box.
We have an embedded python framework we use within our app and it looks like the requests package is being overridden on machines that have installed it (via easy_install or pip). If you uninstall this then the uploads should work again:
To do so, run this from a terminal: pip uninstall requests
sudo may be needed if pip complains about permissions, in which case it would be sudo pip uninstall requests
The next version will correct this so that uninstalling will not be necessary.