Allow easily silencing the server log during tests

src/calibre/srv/tests/base.py

@@ -86,6 +86,7 @@ class TestServer(Thread):
             log=ServerLog(level=ServerLog.WARN),
         )
         self.log = self.loop.log
+        self.silence_log = self.log
         specialize(self)
 
     def setup_defaults(self, kwargs):

src/calibre/utils/logging.py

@@ -159,6 +159,13 @@ class Log(object):
     def __call__(self, *args, **kwargs):
         self.prints(INFO, *args, **kwargs)
 
+    def __enter__(self):
+        self.orig_filter_level = self.filter_level
+        self.filter_level = self.ERROR + 100
+
+    def __exit__(self, *args):
+        self.filter_level = self.orig_filter_level
+
 class DevNull(Log):
 
     def __init__(self):