Custom fallback text in emails for galleries that require JavaScript

Hi all,

I have a small personal blog, and I use the default Jetpack newsletter module to send my posts to subscribers.

This week I published a post that includes a slideshow gallery ([gallery link="none" type="slideshow" ids=""]), and I noticed that the email shows a fallback text “the slideshow requires JavaScript” (since my settings are in Spanish, it shows up as “El pase de diapositivas requiere JavaScript.”).

I’m trying to find a way to customize that fallback text so it’s a bit friendlier. Not just to match the tone of my writing, but because my subscribers (ie my mom) have no idea what that means. Something like “There is a cool photo gallery here but it doesn’t work on emails, visit the post [link] to see it!” would be a lot more helpful.

Is there a way to customize this somewhere in Jetpack’s settings, it with a custom function in a plugin?