Add a unit test for TemplateHook.render_to_string().

Review Request #9658 — Created Feb. 17, 2018 and submitted — Latest diff uploaded

Information

Djblets
release-1.0.x
2d14608...

Reviewers

The unit tests for TemplateHook lacked a proper test for
render_to_string(). This adds a basic test for this, ensuring that
string rendering works as expected.

Unit tests pass.