KF5 - An install error message too difficult for me

While installing plasma 5 from tsaop in crux-3.4-rc2, I have been obliged to halt by the following message: Traceback (most recent call last):     File "/usr/bin/gtkdoc-rebase", line 28, in <module>        from gtkdoc import common, config, rebase     File "/usr/share/gtk-doc/python/gtkdoc/common.py", line 31, in <module>        import six ImportError: No module named six. As far as at this moment, the halt blocked install of networkmanager and libnotify. I found similar messages while googling, but no clear indication of its meaning. I would be grateful for an help about how to proceed. Thanks.