patch.
-- [[chrysn]]
+
+> update 2014-06-29: the problem persists, but i found it is not trivial to
+> reproduce. to demonstrate, use this test plugin:
+>
+> #!/usr/bin/env python
+> # -*- coding: utf-8 -*-
+>
+> from proxy import IkiWikiProcedureProxy
+>
+> def preprocess(self, proxy, *args):
+> return repr(self.rpc('pagetype', 'schön'))
+>
+> proxy = IkiWikiProcedureProxy(__name__)
+> proxy.hook('preprocess', preprocess, id='testdirective')
+> proxy.run()
+>
+> note that when the 'schön' is stored in a variable, the exception changes --
+> it seems to me that the issue is related to the way exceptions are encoded.
+>
+> the suggested patch still applies and solves the issue. --[[chrysn]]
should be safe for inclusion.
--[[chrysn]]
+
+> update 2014-06-29: the patch still applies and fixes the issue. in the
+> meantime, i noticed that the desired effect doesn't happen when no explicit
+> size is set. as scalable graphics don't necessarily have a natural size
+> anyway, i don't consider that a showstopper. --[[chrysn]]