Merge pull request #2850 from wking/localinterfaces-localhost

Consolidate host IP detection in utils.localinterfaces

This PR replaces a number of hard-coded 127.0.0.1 references with
LOCALHOST, and consolidates the computation of LOCALHOST,
LOCAL_IPS, and a new PUBLIC_IPS in the localinterfaces module.

It's unclear to me when LOCALHOST would not be 127.0.0.1. I suppose
you could have another IP in the 127.0.0.0/8 block, or a IPv6 address.
It may also be possible to not have a loopback interface at all. In
that case it's possible that we need a LOOPBACK variable in
utils.localinterfaces which is a valid loopback interface or None, so
that consumers can differentiate between generic IPs pointing back to
the local host and the loopback interface.

IPython/frontend/html/notebook/notebookapp.py

@@ -70,6 +70,7 @@ from IPython.zmq.ipkernel import (
     IPKernelApp
 )
 from IPython.utils.importstring import import_item
+from IPython.utils.localinterfaces import LOCALHOST
 from IPython.utils.traitlets import (
     Dict, Unicode, Integer, List, Enum, Bool,
     DottedObjectName
@@ -87,9 +88,6 @@ _notebook_id_regex = r"(?P<notebook_id>\w+-\w+-\w+-\w+-\w+)"
 _profile_regex = r"(?P<profile>[^\/]+)" # there is almost no text that is invalid
 _cluster_action_regex = r"(?P<action>start|stop)"
 
-
-LOCALHOST = '127.0.0.1'
-
 _examples = """
 ipython notebook                       # start the notebook
 ipython notebook --profile=sympy       # use the sympy profile
@@ -610,7 +608,7 @@ class NotebookApp(BaseIPythonApplication):
         info("Use Control-C to stop this server and shut down all kernels.")
 
         if self.open_browser or self.file_to_run:
-            ip = self.ip or '127.0.0.1'
+            ip = self.ip or LOCALHOST
             try:
                 browser = webbrowser.get(self.browser or None)
             except webbrowser.Error as e: