Still intermittent test failures in test_wait_script_waits_for_lldpd

This happens for me once every few hundred times the test runs. Besides the one expected call to time.sleep, the injected Mock reports hundreds of additional calls, with a timeout of 0.1 seconds. It doesn't seem to be anything in our codebase as such.

The extra calls seem to be coming from Crochet. When I inject an error into the additional time.sleep calls (but not the ones the call expects), I find this:

Exception in thread Thread-1:
Traceback (most recent call last):
  File "/usr/lib/python2.7/threading.py", line 810, in __bootstrap_inner
    self.run()
  File "build/bdist.linux-x86_64/egg/crochet/_shutdown.py", line 28, in run
    time.sleep(0.1)

Patching is of course not thread-safe. It's a wonder this isn't affecting more tests. We can probably work around the failure for now by importing the sleep function from time, instead of importing the time module and using its sleep function.

Whoops. Not as easy as it sounds. The function that's being tested is special: it can't use any imports from the rest of its module. So the tests need to inject into imports that happen inside the function.