Ignore teardown failure if it's caused by removing missing file or directory

[chying]

Summary

This is aiming to workaround this issue:
When test is decorated with expectedFlakey* and has teardown hook attached, the teardown hook will be added and executed twice,
the second execution will fail due to "missing file".

[vharron]

Maybe we should call teardown from expectedFlakey instead?

[tberghammer]

I agree that we should call a tear-down after each run of the test case because without it the 2 run might effect each other. Also the same is true for calling set-up before each run.

[chying]

Based on feedback, handle teardown and setup inside of expectedFlakey function.
Don't run retry if the test case is already marked as xfail or skip.

[tberghammer]

LGTM

lldb/trunk/test/lldbtest.py

 def expectedFlakey(expected_fn, bugnumber=None):
     def expectedFailure_impl(func):
         @wraps(func)
         def wrapper(*args, **kwargs):
             from unittest2 import case
             self = args[0]
             try:
                 func(*args, **kwargs)
+            # don't retry if the test case is already decorated with xfail or skip
+            except (case._ExpectedFailure, case.SkipTest, case._UnexpectedSuccess):
+                raise
             except Exception:
                 if expected_fn(self):
-                    # retry
+                    # before retry, run tearDown for previous run and setup for next
                     try:
+                        self.tearDown()
+                        self.setUp()
                         func(*args, **kwargs)
                     except Exception:
                         # oh snap! two failures in a row, record a failure/error
                         raise
                     # record the expected failure
                     raise case._ExpectedFailure(sys.exc_info(), bugnumber)
                 else:
                     raise