Add test util to mute output to stdout

Used by the tests of the autoadmin app.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

mayan/apps/common/tests/utils.py

@@ -0,0 +1,16 @@
+from contextlib import contextmanager
+import sys
+
+
+class NullFile(object):
+    def write(self, string):
+        """Writes here go nowhere"""
+
+
+@contextmanager
+def mute_stdout():
+    stdout_old = sys.stdout
+    sys.stdout = NullFile()
+    yield
+    sys.stdout = stdout_old
+