The `__future__` we relied on is now, where the 3 specific things are
all included [since Python 3.0](https://docs.python.org/3/library/__future__.html):
* absolute_import
* print_function
* unicode_literals
* division
These import statements are no-ops and are no longer necessary.
Running shell commands using Swift in simulator tests is hard. We change the mechanism so that
BuildModulesFromGraph.swift prints command line arguments and a simple python script
picks these arguments and actually runs the command.