diff --git a/Lib/logging/config.py b/Lib/logging/config.py
index 1e5ff68..63193b1 100644
--- a/Lib/logging/config.py
+++ b/Lib/logging/config.py
@@ -386,15 +386,21 @@
         """
         name = s.split('.')
         used = name.pop(0)
-        found = self.importer(used)
-        for frag in name:
-            used += '.' + frag
-            try:
-                found = getattr(found, frag)
-            except AttributeError:
-                self.importer(used)
-                found = getattr(found, frag)
-        return found
+        try:
+            found = self.importer(used)
+            for frag in name:
+                used += '.' + frag
+                try:
+                    found = getattr(found, frag)
+                except AttributeError:
+                    self.importer(used)
+                    found = getattr(found, frag)
+            return found
+        except ImportError:
+            e, tb = sys.exc_info()[1:]
+            v = ValueError('Cannot resolve %r: %s' % (s, e))
+            v.__cause__, v.__traceback__ = e, tb
+            raise v
 
     def ext_convert(self, value):
         """Default converter for the ext:// protocol."""
@@ -873,6 +879,8 @@
         def run(self):
             server = self.rcvr(port=self.port, handler=self.hdlr,
                                ready=self.ready)
+            if self.port == 0:
+                self.port = server.server_address[1]
             self.ready.set()
             global _listener
             logging._acquireLock()
diff --git a/Lib/test/test_logging.py b/Lib/test/test_logging.py
index c884d3e..d763459 100644
--- a/Lib/test/test_logging.py
+++ b/Lib/test/test_logging.py
@@ -1670,6 +1670,8 @@
         t = logging.config.listen(port)
         t.start()
         t.ready.wait()
+        # Now get the port allocated
+        port = t.port
         t.ready.clear()
         try:
             sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)