Add support for AsyncMappingKernelManager

Supports running against incompatible jupyter_client so long as the
desired kernel_manager_class is not `AsyncMappingKernelManager`.

notebook/notebookapp.py

@@ -37,7 +37,6 @@
 except ImportError: #PY2
     from base64 import encodestring as encodebytes
 
-
 from jinja2 import Environment, FileSystemLoader
 
 from notebook.transutils import trans, _
@@ -78,7 +77,7 @@
 
 from .base.handlers import Template404, RedirectWithParams
 from .log import log_request
-from .services.kernels.kernelmanager import MappingKernelManager
+from .services.kernels.kernelmanager import MappingKernelManager, AsyncMappingKernelManager, MappingKernelManagerBase
 from .services.config import ConfigManager
 from .services.contents.manager import ContentsManager
 from .services.contents.filemanager import FileContentsManager
@@ -1138,6 +1137,7 @@ def _update_mathjax_config(self, change):
 
     kernel_manager_class = Type(
         default_value=MappingKernelManager,
+        klass=MappingKernelManagerBase,
         config=True,
         help=_('The kernel manager class to use.')
     )
@@ -1349,6 +1349,13 @@ def init_configurables(self):
             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.")
+
         self.contents_manager = self.contents_manager_class(
             parent=self,
             log=self.log,