Take a django.core.mail email message and replace any MEDIA_URL-served images with attached images
The code here will take an EmailMessage from django.core.mail and replace the sourcing of any images served by the application with attached image content. Note: This expects a valid closing tag of **/>** on img elements, it will not properly handle filenames with **'** characters in it, and it does not handle if invalid image sources are listed.
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