The diff viewer now interfaces with the new code safety checkers,

looking for unsafe content during diff generation, before anyone but the

owner is able to view the diff.
Scanners are run per-line, and any warnings or errors from the checker

will be stored along with that line and in a global list in the chunk

generator.
Anything found on a line will cause that line to display a red warning

symbol. Hovering over that will show a summary of what was found. The

top of the file will also show an alert from the safety checker

detailing what was found.
The per-line and per-file information is also available through the Diff

Context API, since it's just part of the resulting file/chunk

information.
The current trojan code safety checker we have deals with

possibly-malicious Unicode characters. As such, there's also support for

highlighting these characters, using a new CSS component, rb-o-duc.

DUCs are Displayed Unicode Characters. They are a simple <span>

containing the codepoint and the character entity.
DUCs default to safely showing the codepoint in a little box, instead of

rendering the character. They can be toggled to render instead, by

setting the -hide-ducs CSS modifier class on the .sidebyside element

for the diff viewer. The render toggling happens purely in CSS.
Hovering over a DUC will show information on the Unicode character. Note

that DUCs are not provided for all Unicode characters, only those that a

code safety checker has highlighted.
The trojan code checker provides the button used for toggling those

characters.

Unit tests pass on Python 2 and 3.
Tested this with the Trojan Source code checker, using the source files

at https://github.com/nickboucher/trojan-source/