When imghdr fails to deduce the image type, use file extension

[dismantl]

Status

Ready for review

Description of Changes

I ran into what might be an edge case, where imghdr.what() failed to figure out the filetype of a submitted photo. So I added in this little snippet in case imghdr fails, to determine image type using the filename.

I'm not really sure what a good way to add tests for this is, since I don't really know why imghdr failed for this particular image. For reference, the image was https://bpdwatch.s3.amazonaws.com/8d/095b8184d1d4abd90e867a8b2d41961bcc4fbd2b42e2af6f0ad8c80ca44fc7.jpg

Notes for Deployment

Screenshots (if appropriate)

Tests and linting

• I have rebased my changes on current develop

• pytests pass in the development environment on my local machine

• flake8 checks pass

[redshiftzero]

just checked the extensions here, lgtm

I think we could add test coverage with some test files for each extension but this is good to merge as is