slot: If an exception is caught during disconnect() while we're already handling an exception, print the second exception but continue raising the first one.
Operator: Added support for the special NOTREADY metadict attribute, which can be used by an operator during setupOutputs to specify that a specific slot is not actually ready, despite the fact that setupOutputs completed without any errors.
OpSingleChannelSelector: In setupOutputs, Output.meta.NOTREADY if there aren't enough input channels to provide output yet.
schematic: Color-code slots according to their ready status
OpVigraWatershedViewer: Added a fixme.