Code review comment for lp:~bac/launchpad/bug-341935-captcha

= Summary =

Bug 341935 addresses the need to do *something* to disrupt the ability for bots to
trick Launchpad into sending registration email to unsuspecting people. It was
agreed to do a simple, text-based math problem captcha as a first step to try to
defeat the bots. While it would be trivial for bots to defeat this captcha (see the
pagetest!) it is our belief that we are not a real target so no one would invest in a
custom solution for use against Launchpad.

== Proposed fix ==

Add a simple captcha into the form.

== Pre-implementation notes ==

Discussions with Barry and Curtis.

== Implementation details ==

The view for the login page is a mess. It's not a LaunchpadFormView so the additions
were done 'by hand'.

In order to make it a low bar the math question is simple addition with the answer
being in the range [10, 20].

Screenshot at http://people.canonical.com/~bac/captcha.png

== Tests ==

bin/test xx-createaccount.txt

== Demo and Q/A ==

https://launchpad.dev/+login

= Launchpad lint =

Checking for conflicts. and issues in doctests and templates.
Running jslint, xmllint, pyflakes, and pylint.
Using normal rules.

Linting changed files:
  lib/canonical/launchpad/templates/launchpad-login.pt
  lib/lp/registry/stories/foaf/xx-createaccount.txt
  lib/canonical/launchpad/webapp/login.py