Implemented @test.skip_unless and @test.skip_if functionality in nova/test.py.

Added nova/tests/test_skip_examples.py which contains example skip case usages.

nova/test.py

@@ -60,11 +60,42 @@ class skip_test(object):
         self.message = msg
 
     def __call__(self, func):
+        @functools.wraps(func)
         def _skipper(*args, **kw):
             """Wrapped skipper function."""
             raise nose.SkipTest(self.message)
-        _skipper.__name__ = func.__name__
-        _skipper.__doc__ = func.__doc__
+        return _skipper
+
+
+class skip_if(object):
+    """Decorator that skips a test if contition is true."""
+    def __init__(self, condition, msg):
+        self.condition = condition
+        self.message = msg
+
+    def __call__(self, func):
+        @functools.wraps(func)
+        def _skipper(*args, **kw):
+            """Wrapped skipper function."""
+            if self.condition:
+                raise nose.SkipTest(self.message)
+            func(*args, **kw)
+        return _skipper
+
+
+class skip_unless(object):
+    """Decorator that skips a test if condition is not true."""
+    def __init__(self, condition, msg):
+        self.condition = condition
+        self.message = msg
+
+    def __call__(self, func):
+        @functools.wraps(func)
+        def _skipper(*args, **kw):
+            """Wrapped skipper function."""
+            if not self.condition:
+                raise nose.SkipTest(self.message)
+            func(*args, **kw)
         return _skipper