diff --git a/artiq/master/worker_db.py b/artiq/master/worker_db.py
index 0226e995e..45c5e657f 100644
--- a/artiq/master/worker_db.py
+++ b/artiq/master/worker_db.py
@@ -119,9 +119,7 @@ class DeviceError(Exception):
 class DeviceManager:
     """Handles creation and destruction of local device drivers and controller
     RPC clients."""
-    def __init__(self, ddb, virtual_devices=None):
-        if virtual_devices is None:
-            virtual_devices = dict()
+    def __init__(self, ddb, virtual_devices=dict()):
         self.ddb = ddb
         self.virtual_devices = virtual_devices
         self.active_devices = OrderedDict()
@@ -158,28 +156,6 @@ class DeviceManager:
             self.active_devices[name] = dev
             return dev
 
-    def pause_devices(self):
-        """Pauses all active devices, in the opposite order as they were
-        requested."""
-        for dev in reversed(list(self.active_devices.values())):
-            if hasattr(dev.__class__, "pause"):
-                try:
-                    dev.pause()
-                except:
-                    logger.warning("Exception when pausing device %r", dev,
-                                   exc_info=True)
-
-    def resume_devices(self):
-        """Resumes all active devices, in the same order as they were
-        requested."""
-        for dev in self.active_devices.values():
-            if hasattr(dev.__class__, "resume"):
-                try:
-                    dev.resume()
-                except:
-                    logger.warning("Exception when resuming device %r", dev,
-                                   exc_info=True)
-
     def close_devices(self):
         """Closes all active devices, in the opposite order as they were
         requested."""
@@ -187,11 +163,10 @@ class DeviceManager:
             try:
                 if isinstance(dev, (Client, BestEffortClient)):
                     dev.close_rpc()
-                elif hasattr(dev.__class__, "close"):
+                elif hasattr(dev, "close"):
                     dev.close()
-            except:
-                logger.warning("Exception when closing device %r", dev,
-                               exc_info=True)
+            except Exception as e:
+                logger.warning("Exception %r when closing device %r", e, dev)
         self.active_devices.clear()