From a comment by @gasman on #1684:
> It appears the try/catch in ImageEmbedHandler was added here: 74b9f43
>
> Since the rest of the commit doesn't deal with images at all, and the
> commit makes it clear that the corresponding change to
> MediaEmbedHandler was intended to preserve the existing 'fail
> silently' behaviour in the light of the new exceptions added for media
> embeds - I think this try/catch is redundant. `Format.image_to_html`
> does its own catching of image IO errors, which seems to be
> sufficiently robust (if it wasn't, we'd be seeing errors on front-end
> page rendering), so I think this try/catch can reasonably be deleted.
https://github.com/torchbox/wagtail/pull/1684#issuecomment-140695060
98f37bb6ff