Embedded images do not print if referenced as html

**Describe the bug**

Notebooks can have embedded images. These images work just fine if they are referenced via markdown. However if they are referenced using html they display fine but they do not print.

As an example, suppose that you have a notebook and that you insert in a cell an image named `new.jpg`. This gives you the following markdown:
```
```
that works just fine.

However if you try to use that figure changing the above into what should be the equivalent html (e.g. to get more control over the image size, centering, etc.) as in
```

```
that works correctly *on screen* but when you try to print using the File->Print feature, the image is broken in the preview and in the printout.

The issue is present both with `jupyter notebook` and with `jupyter lab`.

Reproduce the issue in Jupyter Notebook and JupyterLab using the supplied markdown and HTML attachment references. Start by comparing the on-screen rendering with File→Print preview, then trace the print path for attachment URLs. Done means the embedded image appears in both the preview and printed output.

Written by the indexing model from the issue text.