In preparation for our CDN provider deprecating TLSv1.0 and TLSv1.1 protocols, we have begun rolling brownouts for these protocols for the first ten (10) minutes of each hour.
During that window, clients accessing pypi.python.org with clients that do not support TLSv1.2 will receive an HTTP 403 with the error message "This is a brown out of TLSv1 support. TLSv1 support is going away soon, upgrade to a TLSv1.2+ capable client.".
For users of pip on MacOS/OS X, upgrading to the latest pip should resolve the issue. pip users on other platforms should upgrade their OpenSSL to a version which supports TLSv1.2.
If you have trouble with getting your PyPI client working, file an issue at https://github.com/pypa/packaging-problems/issues