Add a DummyIn::close no-op implementation

The BOD tests are currently forking a process with a server running, and
this attempts to close stdin. Tests were failing due to DummyIn not
implementing the close() method. Adding this simple no-op does the trick
to allow forking and seems like a harmless addition.

test/_common.py

@@ -284,6 +284,9 @@ class DummyIn(object):
         else:
             self.buf.append(s + '\n')
 
+    def close(self):
+        pass
+
     def readline(self):
         if not self.buf:
             if self.out: