The best should be to not create the meta tags in the html code.
The lines 1675 and 1676 containing meta5 and meta6
You need to remove these two lines in basepage.py or comment out them as follows:
> # create additional meta tags
meta = Html("meta", attr=_meta1) + ( Html("meta", attr=_meta2, indent=False), Html("meta", attr=_meta3, indent=False), Html("meta", attr=_meta4, indent=False), # Html("meta", attr=_meta5, indent=False), # Html("meta", attr=_meta6, indent=False), )