An interesting feature of py.test is its ability to distribute the tests across several computers. As long as the computers are reachable through SSH, py.test will be able to drive each computer by sending tests to be performed.
However, this feature relies on the network; if the connection is broken, the slave will not be able to continue working since it is fully driven by the master.
A Buildbot or other continuous integration tools are preferable when a project has large and long running test campaigns. But the py.test distributed model can be used for the ad hoc distribution of tests when you don't have a proper continuous integration pipeline at hand.