Hello!

I noticed a problem with Faces not showing up despite a Face-header
being present in a message. In this particular case,
base64-decode-region failed to decode the header, which had incorrect
(i.e., excessive) padding. A command line and a Web-based decoder
happily ignored the superfluous '='s at the end of the string. Here is
the string in question:

"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===="

The correct number of '='s here is two.

I don't suspect this problem is widespread in other uses of the base64
decoder, so it seems appropriate to me to just patch
gnus-convert-face-to-png to generate the right amount of padding.