Now that email templates are editable, I'd like to add the user's profile picture to the HTML template trhough gravatar. But to do that, I need the email hash, which is not yet available. Can you put it in a template context variable?
You have a parameter "avatar_url" which has URL for a user avatar. It is a regular avatar (if uploaded), gravatar or default avatar, depends on situation.
You do not have to take a gravatar directly.