"Controller appears to be listening on localhost, but not on this machine" warning on debian/ubuntu

Yeah, it's just a warning, low priority. But also an easy fix, maybe? The reason is because the ip_for_host call returns 127.0.1.1 instead of 127.0.0.1

Quoting from the debian reference manual:

For example, "/etc/hosts" looks like the following.

127.0.0.1 localhost
127.0.1.1 <host_name>

The following lines are desirable for IPv6 capable hosts

::1 ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts

Each line starts with a IP address and it is followed by the associated hostname.

The IP address 127.0.1.1 in the second line of this example may not be found on some other Unix-like systems. The Debian Installer creates this entry for a system without a permanent IP address as a workaround for some software (e.g., GNOME) as documented in the bug #719621.

Not sure if needed but there is ipython info:

{'commit_hash': u'b467d487e',
 'commit_source': 'installation',
 'default_encoding': 'UTF-8',
 'ipython_path': '/home/xxxx/miniconda2/lib/python2.7/site-packages/IPython',
 'ipython_version': '5.5.0',
 'os_name': 'posix',
 'platform': 'Linux-4.4.0-112-generic-x86_64-with-debian-stretch-sid',
 'sys_executable': '/home/xxxx/miniconda2/bin/python',
 'sys_platform': 'linux2',
 'sys_version': '2.7.13 |Continuum Analytics, Inc.| (default, Dec 20 2016, 23:09:15) \n[GCC 4.4.7 20120313 (Red Hat 4.4.7-1)]'}

Start by tracing the ip_for_host call mentioned in the report and reproduce the controller warning on Debian or Ubuntu with a 127.0.1.1 hosts entry. Done means the warning no longer incorrectly reports that the controller is not listening on the machine; the issue does not name a file or test to run.