Fix thumbnails generation with DAM Picture import when filename contains accentued characters

java.lang.IllegalArgumentException: '/tmp/mitô.jpg' contains illegal characters. It should match: [a-zA-Z_0-9-.%:/\\ ]+
	at org.nuxeo.ecm.platform.commandline.executor.service.executors.AbstractExecutor.replaceParams(AbstractExecutor.java:87)
	at org.nuxeo.ecm.platform.commandline.executor.service.executors.AbstractExecutor.getParametersString(AbstractExecutor.java:56)
	at org.nuxeo.ecm.platform.commandline.executor.service.executors.ShellExecutor.exec(ShellExecutor.java:59)
	at org.nuxeo.ecm.platform.commandline.executor.service.CommandLineExecutorComponent.execCommand(CommandLineExecutorComponent.java:154)
	at org.nuxeo.ecm.platform.picture.magick.MagickExecutor.execCommand(MagickExecutor.java:43)
	at org.nuxeo.ecm.platform.picture.magick.utils.ImageConverter.convert(ImageConverter.java:35)