Comment 1 for bug 2729

The authentication system used by Launchpad is being used by a number of systems, and more will be added over time. These systems all have different restrictions on what characters are valid. This means that Launchpad needs to ensure that it only accepts passwords that are valid on all these systems. The most restrictive specification is HTTP Basic Authentication whch dictates a subset of US-ASCII, so this is what we have to restrict passwords to.