How do I upgrade from 14.04 LTS to 16.04.1 LTS?

So, today is July 21st and this page. gives me an option to download 16.04.1 LTS. However, attempting to upgrade gets me this message -

$ sudo do-release-upgrade
Checking for a new Ubuntu release
No new release found

What is wrong? Does it matter that I am running apt-get update behind apt-cacher-ng?

Note: Commenting out the files in apt.conf.d that used apt-cacher-ng did not make a difference.

Edit: Explanation for possible duplicates: Why is "No new release found" when upgrading from a LTS to the next? deals with upgrade from 12.04LTS to 14.04LTS. My question is specific to 14.04 LTS to 16.04.1 LTS upgrade. Old answers, while good for archival purposes are less relevant in a fast changing package like ubuntu. Moreover none of the answers answer what is wrong. The link andrew.46 pointed out is mentioned in one of the comments. This Q & A is more helpful for people upgrading today than the work around mentioned in "Why is "No new release found" when upgrading from a LTS to the next?".

This is an issue that has appeared before: 4 years ago when upgrading from 12.04 LTS (Precise Pangolin) to 14.04.1 LTS (Trusty Tahr):

It looks like a similar issue exists for the upgrade from 14.04 LTS (Trusty Tahr) to 16.04.1 LTS (Xenial Xerus) with the relevant update log not yet updated. There is a choice of two reasonable solutions at the moment:

1. Wait a little until this document is updated and then upgrade as normal



2. Use the following syntax now:

   
   
   

   sudo do-release-upgrade --devel-release
   

Ubuntu documentation speaks on this option of using the --devel-release or -d option:

For further stability of a LTS release there is a slight change in
behaviour if you are currently running a LTS version. LTS systems are
only automatically considered for an upgrade to the next LTS via
do-release-upgrade with the first point release. So for example 14.04
will only upgrade once 16.04.1 is released. If you want to update

before, e.g. on a subset of machines to evaluate the LTS upgrade for
your setup the same argument as an upgrade to a dev release has to be
used via the -d switch.

And certainly at the moment this should be a safe course to take. When undertaken on my own Trusty system:

andrew@corinth:~$ sudo do-release-upgrade
[sudo] password for andrew: 
Checking for a new Ubuntu release

No new release found
andrew@corinth:~$ sudo do-release-upgrade --devel-release
Checking for a new Ubuntu release
Get:1 Upgrade tool signature [198 B]                                           
Get:2 Upgrade tool [1,265 kB]                                                  
Fetched 1,265 kB in 0s (0 B/s)                                                 
authenticate 'xenial.tar.gz' against 'xenial.tar.gz.gpg' 
extracting 'xenial.tar.gz'
[...]

And the process rolls on installing Xenial by utlising this alternative file. A few hints at upcoming resolution of this issue:

1. A few enquiries in IRC (thanks @ThomasWard) indicate imminent fixing of the issue pending the fixing of any bugs in the upgrade path...


2. A personal email to myself from a developer has indicated that this should be fixed in the week commencing July 25th


3. A Launchpad bug and Feature Request filed on this issue has some interesting comments...

Crossed fingers for a resolution soon!!

Note: The update log altered on July 29th my time, so issue now resolved...

References: