1 files changed, 25 insertions, 0 deletions
diff --git a/Lib/test/test_support.py b/Lib/test/test_support.py
index 82fd5f4..2e47aed 100644
--- a/Lib/test/test_support.py
+++ b/Lib/test/test_support.py
@@ -312,6 +312,31 @@ class EnvironmentVarGuard(object):
         for unset in self._unset:
             del self._environ[unset]
 
+class TransientResource(object):
+
+    """Raise ResourceDenied if an exception is raised while the context manager
+    is in effect that matches the specified exception and attributes."""
+
+    def __init__(self, exc, **kwargs):
+        self.exc = exc
+        self.attrs = kwargs
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, type_=None, value=None, traceback=None):
+        """If type_ is a subclass of self.exc and value has attributes matching
+        self.attrs, raise ResourceDenied.  Otherwise let the exception
+        propagate (if any)."""
+        if type_ is not None and issubclass(self.exc, type_):
+            for attr, attr_value in self.attrs.iteritems():
+                if not hasattr(value, attr):
+                    break
+                if getattr(value, attr) != attr_value:
+                    break
+            else:
+                raise ResourceDenied("an optional resource is not available")
+
 
 #=======================================================================
 # Decorator for running a function in a different locale, correctly resetting