Allow RedirectStdStreams to behave correctly using with. Allow flushing streams.

tests/saltunittest.py

@@ -74,6 +74,7 @@ class RedirectStdStreams(object):
 
     def __enter__(self):
         self.redirect()
+        return self
 
     def __exit__(self, exc_type, exc_value, traceback):
         self.unredirect()
@@ -90,14 +91,33 @@ class RedirectStdStreams(object):
     def unredirect(self):
         if not self.__redirected:
             return
-
+        try:
             self.__stdout.flush()
             self.__stdout.close()
+        except ValueError:
+            # already closed?
+            pass
+        try:
             self.__stderr.flush()
             self.__stderr.close()
+        except ValueError:
+            # already closed?
+            pass
+
         sys.stdout = self.old_stdout
         sys.stderr = self.old_stderr
 
+    def flush(self):
+        if self.__redirected:
+            try:
+                self.__stdout.flush()
+            except:
+                pass
+            try:
+                self.__stderr.flush()
+            except:
+                pass
+
 
 class TestsLoggingHandler(object):
     '''