Unfortunately, the main dev has been saying that he'll be releasing a rewrite with Python 3 support "at the end of the month" for the past 2-3 years. There's actually a fork ("Fabric3") which fully supports both Python 2.7 and Python 3.4+, but the Fabric dev refuses to merge in any PRs that have been submitted to help with Python 3 support. It's somewhat infuriating.

https://github.com/fabric/fabric/pulls?q=is%3Apr+python+3