[magick-users] C++ writeImages() not thread-safe?

[duc.sequere.aut.de.via.decede at imagemagick.org]

> Btw, does the failing tests have to do with the drawing on the Images?

No.  It has to do with the same I/O handler being associated with the
different image sequences.  The patch we provided seems to fix the problem
for you but it causes a few regression tests to fail so we're looking for
a more robust solution.  We will work on this problem over the next few
days/weeks and get back with you.