Comment # 2 on bug 1223381 from Dominique Leuenberger

(In reply to Arvin Schnell from comment #1)
> The build failure does not look related to boost but swig. From
> /usr/share/doc/packages/swig/CHANGES:
> 
> Replace SWIG_Python_str_AsChar with SWIG_PyUnicode_AsUTF8AndSize
> 
> So maybe znc failed to build for a longer time and with the boost
> update the old znc version cannot be linked anymore.

Indeed - Boost was likely 'just' the one that triggered the rebuild as the
package turned uninstallable. Swig did not cause the rebuild to happen