So given that the ecosystem is dropping support for 2.7 in earnest, the time has come for us to start planning for Siphon to move on from Legacy Python: Given these events, and based on preliminary ...

Conda says that siphon and Python 3.5 are in conflict with each other on both linux and mac. It looks like you have 3.5 binaries on anaconda.org, so maybe something specific to how you built them?