The incidence of sdist fetch failures on travis-ci is high enough that it disrupts reasonable efforts to keep the build green. Twitter uses an internal pypi mirror exclusively and Foursquare uses one in preference to pypi which it falls back to. Both companies have success using this strategy under ci. Consider doing something similar using the binary hosting options discussed here: https://rbcommons.com/s/twitter/r/22/