Fix detection of unsupported config, prevent async on 3.5

notebook/notebookapp.py

@@ -1390,14 +1390,16 @@ class NotebookApp(JupyterApp):
             connection_dir=self.runtime_dir,
             kernel_spec_manager=self.kernel_spec_manager,
         )
-        #  Ensure the appropriate jupyter_client is in place.
+        #  Ensure the appropriate version of Python and jupyter_client is available.
         if isinstance(self.kernel_manager, AsyncMappingKernelManager):
+            if sys.version_info < (3, 6):
+                raise ValueError("You are using `AsyncMappingKernelManager` in Python 3.5 (or lower) "
+                                 "which is not supported. Please upgrade Python to 3.6+ or change kernel managers.")
             if not async_kernel_mgmt_available:
                 raise ValueError("You are 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 to use '{}'.".
-                              format(self.kernel_manager.__class__.__name__))
+                                 "jupyter_client installed!  Please upgrade jupyter_client or change kernel managers.")
+            self.log.info("Asynchronous kernel management has been configured to use '{}'.".
+                          format(self.kernel_manager.__class__.__name__))
 
         self.contents_manager = self.contents_manager_class(
             parent=self,

notebook/services/kernels/kernelmanager.py

@@ -35,7 +35,8 @@ try:
 except ImportError:
     class AsyncMultiKernelManager(object):
         """Empty class to satisfy unused reference by AsyncMappingKernelManager."""
-        pass
+        def __init__(self, **kwargs):
+            pass
 
 
 class MappingKernelManager(MultiKernelManager):

notebook/services/kernels/tests/test_kernels_api.py

@@ -1,6 +1,7 @@
 """Test the kernels service API."""
 
 import json
+import sys
 import time
 
 from traitlets.config import Config
@@ -198,6 +199,14 @@ class KernelAPITest(NotebookTestBase):
 class AsyncKernelAPITest(KernelAPITest):
     """Test the kernels web service API using the AsyncMappingKernelManager"""
 
+    @classmethod
+    def setup_class(cls):
+        if not async_testing_enabled:
+            raise SkipTest("AsyncKernelAPITest tests skipped due to down-level jupyter_client!")
+        if sys.version_info < (3, 6):
+            raise SkipTest("AsyncKernelAPITest tests skipped due to Python < 3.6!")
+        super(AsyncKernelAPITest, cls).setup_class()
+
     @classmethod
     def get_argv(cls):
         argv = super(AsyncKernelAPITest, cls).get_argv()
@@ -209,12 +218,6 @@ class AsyncKernelAPITest(KernelAPITest):
                         'notebook.services.kernels.kernelmanager.AsyncMappingKernelManager'])
         return argv
 
-    def setUp(self):
-        if not async_testing_enabled:
-            raise SkipTest("AsyncKernelAPITest.{test_method} skipped due to down-level jupyter_client!".
-                           format(test_method=self._testMethodName))
-        super(AsyncKernelAPITest, self).setUp()
-
 
 class KernelFilterTest(NotebookTestBase):
 

notebook/services/sessions/tests/test_sessions_api.py

@@ -5,8 +5,8 @@ from functools import partial
 import io
 import os
 import json
-import requests
 import shutil
+import sys
 import time
 
 from unittest import SkipTest
@@ -269,6 +269,14 @@ class SessionAPITest(NotebookTestBase):
 class AsyncSessionAPITest(SessionAPITest):
     """Test the sessions web service API using the AsyncMappingKernelManager"""
 
+    @classmethod
+    def setup_class(cls):
+        if not async_testing_enabled:
+            raise SkipTest("AsyncSessionAPITest tests skipped due to down-level jupyter_client!")
+        if sys.version_info < (3, 6):
+            raise SkipTest("AsyncSessionAPITest tests skipped due to Python < 3.6!")
+        super(AsyncSessionAPITest, cls).setup_class()
+
     @classmethod
     def get_argv(cls):
         argv = super(AsyncSessionAPITest, cls).get_argv()
@@ -280,9 +288,3 @@ class AsyncSessionAPITest(SessionAPITest):
                         'notebook.services.kernels.kernelmanager.AsyncMappingKernelManager'])
 
         return argv
-
-    def setUp(self):
-        if not async_testing_enabled:
-            raise SkipTest("AsyncSessionAPITest.{test_method} skipped due to down-level jupyter_client!".
-                           format(test_method=self._testMethodName))
-        super(AsyncSessionAPITest, self).setUp()