It seems that this bug is caused by the following one. Remove swig 2.0 for Stretch (python 3.5, octave 4.0 unsupported) https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=786517
As this bug is not resolved until 4/20 autoremoval deadline, it affects
transitively
depended package such as fcitx and so on.
To fix this issue, just to use swig3.0 because swig 3.0 has
backward compatibility for presage.
Build-Depends:
swig3.0 | swig2.0 (>= 2.0.4),
Regards,
