Enhance slipstream.bootstrap when started with Python 3 (#305)
Enhance slipstream.bootstrap when started with Python 3 (#305)

* slipstream.bootstrap: Do not retry to find a package manager.

* slipstream.bootstrap: If Python 2 is not installed, install it and rerun the bootstrap with Python 2.

See #304

slipstream/SlipStreamClient,slipstream/SlipStreamClient