Indicate that async kernel management is configured

Author: kevin-bates

notebook/notebookapp.py

@@ -108,6 +108,13 @@
 from ._tz import utcnow, utcfromtimestamp
 from .utils import url_path_join, check_pid, url_escape, urljoin, pathname2url
 
+# Check if we can user async kernel management
+try:
+    from jupyter_client import AsyncMultiKernelManager
+    async_kernel_mgmt_available = True
+except ImportError:
+    async_kernel_mgmt_available = False
+
 #-----------------------------------------------------------------------------
 # Module globals
 #-----------------------------------------------------------------------------
@@ -1375,18 +1382,21 @@ def init_configurables(self):
         self.kernel_spec_manager = self.kernel_spec_manager_class(
             parent=self,
         )
+
         self.kernel_manager = self.kernel_manager_class(
             parent=self,
             log=self.log,
             connection_dir=self.runtime_dir,
             kernel_spec_manager=self.kernel_spec_manager,
         )
         #  Ensure the appropriate jupyter_client is in place.
-        #  TODO: remove once dependencies are updated.
         if isinstance(self.kernel_manager, AsyncMappingKernelManager):
-            if not hasattr(self.kernel_manager, 'list_kernel_ids'):
-                raise RuntimeError("Using `AsyncMappingKernelManager` without an appropriate "
-                                   "jupyter_client installed!  Upgrade jupyter_client and try again.")
+            if not async_kernel_mgmt_available:
+                raise ValueError("You're using `AsyncMappingKernelManager` without an appropriate "
+                                 "jupyter_client installed!  Upgrade jupyter_client or change kernel managers.")
+            else:
+                self.log.info("Asynchronous kernel management has been configured via '{}'.".
+                              format(self.kernel_manager.__class__.__name__))
 
         self.contents_manager = self.contents_manager_class(
             parent=self,

notebook/services/kernels/kernelmanager.py

@@ -35,6 +35,7 @@
     from jupyter_client.multikernelmanager import AsyncMultiKernelManager
 except ImportError:
     class AsyncMultiKernelManager(object):
+        """Empty class to satisfy unused reference by AsyncMappingKernelManager."""
         pass
 
 
@@ -46,8 +47,6 @@ class MappingKernelManagerBase(LoggingConfigurable):
 
         Since we have this class, we'll reduce duplication of code between the disjoint classes by using this
         common superclass for configuration properties and static methods and local member variables.
-
-        TODO - move contents back to appropriate mapping kernel manager once we converge to async only.
     """
 
     kernel_argv = List(Unicode())