Removing 32-bit architectures from juju-core source package

[Nicholas Skaggs]

Hello all. I'd like to discuss the removal of 32-bit architectures from 
the juju-core source package. The current packaging in the xenial and 
yakkety archive for juju-core specifies it's architecture as 'All'. This 
was an oversight as we officially support only the following architectures:

amd64 ppc64el arm64 s390x

We don't test or support 32-bit builds of juju. This is in-line with the 
clouds upon which juju runs which don't support 32-bit servers, as well 
as our own support of xenial server and mitaka -- 64-bit only.

With this in mind, I'd like to update the archive packaging in both 
xenial and yakkety to remove these unsupported builds. I realize 
removing previously published binaries from the xenial archive isn't 
ideal, however we cannot update the current packages in order to deal 
with changes in cloud providers.

I am looking for feedback and help to accomplish this. I would propose 
the following, but am open to other ideas to best accomplish this task.

1) Upload a new conjure-up package to xenial and yakkety that changes 
the architecture to 'Any'
2) Upload a new juju-source package to xenial and yakkety that:
         -- specifies the architecture as 'amd64 ppc64el arm64 s390x'
         -- provides a second binary package for 32-bit users that 
ensures they upgrade to a message informing them the package isn't 
supported.

I want to ensure a smooth experience for anyone who installed a 32-bit 
version of juju on xenial. It is not found on any images, and juju 
itself is not yet final. Production deployments should still be 
utilizing juju-1. I would like to remove this package before wider 
adoption as juju2 enters RC and final release stages. I would especially 
appreciate ideas about ensuring a good upgrade story for current users. 
I don't suspect there are many at all, but I don't want to leave 
unsupported and abandoned packages in the archive.

Nicholas