[AIRFLOW-2115] Fix doc links to PythonHosted

Replaced `http://pythonhosted.org/airflow/` links
to `https://airflow.incubator.apache.org/` in:
- Airflow Web UI
- `default_airflow.cfg` file
- Tutorial
- `CONTRIBUTING.md`

Closes #3050 from kaxil/AIRFLOW-2115

CONTRIBUTING.md

@@ -65,7 +65,7 @@ If you are proposing a feature:
 
 ## Documentation
 
-The latest API documentation is usually available [here](http://pythonhosted.org/airflow).
+The latest API documentation is usually available [here](https://airflow.incubator.apache.org/).
 To generate a local version, you need to have installed airflow with
 the `doc` extra. In that case you can generate the doc by running:
 

airflow/config_templates/default_airflow.cfg

@@ -224,7 +224,7 @@ error_logfile = -
 expose_config = False
 
 # Set to true to turn on authentication:
-# http://pythonhosted.org/airflow/security.html#web-authentication
+# https://airflow.incubator.apache.org/security.html#web-authentication
 authenticate = False
 
 # Filter the list of dags by owner name (requires authentication to be enabled)

airflow/example_dags/tutorial.py

@@ -15,7 +15,7 @@
 """
 ### Tutorial Documentation
 Documentation that goes along with the Airflow tutorial located
-[here](http://pythonhosted.org/airflow/tutorial.html)
+[here](https://airflow.incubator.apache.org/tutorial.html)
 """
 import airflow
 from airflow import DAG

airflow/www/app.py

@@ -103,10 +103,11 @@ def create_app(config=None, testing=False):
 
         admin.add_link(base.MenuLink(
             category='Docs', name='Documentation',
-            url='http://pythonhosted.org/airflow/'))
+            url='https://airflow.incubator.apache.org/'))
         admin.add_link(
             base.MenuLink(category='Docs',
-                name='Github',url='https://github.com/apache/incubator-airflow'))
+                          name='Github',
+                          url='https://github.com/apache/incubator-airflow'))
 
         av(vs.VersionView(name='Version', category="About"))
 

docs/plugins.rst

@@ -130,7 +130,7 @@ definitions in Airflow.
     ml = MenuLink(
         category='Test Plugin',
         name='Test Menu Link',
-        url='http://pythonhosted.org/airflow/')
+        url='https://airflow.incubator.apache.org/')
 
     # Defining the plugin class
     class AirflowTestPlugin(AirflowPlugin):

tests/plugins/test_plugin.py

@@ -58,7 +58,8 @@ def test(self):
 ml = MenuLink(
     category='Test Plugin',
     name='Test Menu Link',
-    url='http://pythonhosted.org/airflow/')
+    url='https://airflow.incubator.apache.org/')
+
 
 # Defining the plugin class
 class AirflowTestPlugin(AirflowPlugin):