invalid datetime attributes

[cfm]

Description

In securedrop/source_templates/lookup.html, time elements have invalid datetime attributes giving too many digits for fractional seconds.

Steps to Reproduce

Validate the HTML of the Source Interface's /lookup view.

Expected Behavior

The page validates.

Actual Behavior

The page fails validation with errors like:

Bad value 2021-07-13 22:47:04.564322 for attribute datetime on element time: A fraction of a second must be one, two, or three digits

Comments

Should be simple to fix with a truncating Jinja filter.

[anorthall]

I have fixed this in #6058, however I used strftime() instead of the Jinja truncate feature, as you cannot truncate the datetime instance without first converting it to a string.

[zenmonkeykstop]

Thanks to @cfm for finding this and @anorthall for picking it up! Will add a comment on the PR.