Suppress "WARNING: unknown mimetype for ..." when building epub #3391

[pdurbin]

RFI Checklist

1. Related Issues

• Connects to Guides - Building epub version results in warnings #3391 Guides - Building epub version results in warnings

---

2. Pull Request Checklist

• Functionality completed as described in FRD. No FRD.
• Dependencies, risks, assumptions in FRD addressed. No FRD.
• Unit tests completed. None
• Deployment requirements identified (e.g., SQL scripts, indexing) Requires Sphinx 1.5.1 or higher per "WARNING: unknown mimetype for [filename] ignoring" when running make epub sphinx-doc/sphinx#3214
• Documentation completed. None.
• All code checkins completed

---

3. Review Checklist

After the pull request has been submitted, fill out this section.

• Code review completed or waived
• Testing requirements completed
• Usability testing completed or waived
• Support testing completed or waived
• Merged with develop branch and resolved conflicts

[coveralls]

Coverage remained the same at 8.689% when pulling 56db0a8 on 3391-suppress-epub-warnings into 52e9ec3 on develop.