This is a plugin which will terminate tests after a certain timeout.
When doing so it will show a stack dump of all threads running at the
time. This is useful when running tests under a continuous
integration server or simply if you don't know why the test suite
hangs.

Note that while by default on POSIX systems py.test will continue to
execute the tests after a test has timed, out this is not always
possible. Often the only sure way to interrupt a hanging test is by
terminating the entire process. As this is a hard termination
(``os._exit()``) it will result in no teardown, JUnit XML output etc.
But the plugin will ensure you will have the debugging output on
stderr nevertheless, which is the most important part at this stage.
See below for detailed information on the timeout methods and their
side-effects.