#1698 Handle unindentifiable images without erroring
I don't have an example to duplicate it, but you could try interlaced and non-interlaced PNGs, or just fake it.
Module allura.model.filesystem:149 in save_image
<< return None, None
image = Image.open(fp)
format = image.format
if save_original:
>> image = Image.open(fp)
Module Image:1980 in open
<< pass
raise IOError("cannot identify image file")
#
>> raise IOError("cannot identify image file")
IOError: cannot identify image file
Fixing with [#4726]