require Python 3.5

3.4 doesn't have isawaitable

remove unsupported combinations from test matrix

Author: minrk

.travis.yml

@@ -68,10 +68,6 @@ matrix:
           dist: xenial  # required for Python >= 3.7 (travis-ci/travis-ci#9069)
         - python: 3.6
           env: GROUP=docs
-        - python: 3.6
-          env:
-          - GROUP=python
-          - EXTRA_PIP="tornado<5"
 
 after_success:
     - codecov

jupyter_server/services/sessions/sessionmanager.py

@@ -241,8 +241,8 @@ def row_to_model(self, row, tolerate_culled=False):
         if row['type'] == 'notebook':
             # Provide the deprecated API.
             model['notebook'] = {'path': row['path'], 'name': row['name']}
-        return model
-
+        raise gen.Return(model)
+    
     def list_sessions(self):
         """Returns a list of dictionaries containing all the information from
         the session database"""
@@ -256,7 +256,7 @@ def list_sessions(self):
                 result.append(model)
             except KeyError:
                 pass
-        return result
+        raise gen.Return(result)
 
     @gen.coroutine
     def delete_session(self, session_id):

setup.py

@@ -95,7 +95,7 @@
                  'nbval', 'nose-exclude', 'selenium', 'pytest', 'pytest-cov'],
         'test:sys_platform == "win32"': ['nose-exclude'],
     },
-    python_requires='>=3.5',
+    python_requires = '>=3.5',
     entry_points = {
         'console_scripts': [
             'jupyter-server = jupyter_server.serverapp:main',