The first panel consisted entirely of CPython core developers. The lack of gender diversity on that panel had nothing to do with the conference organisers, it was an accurate reflection of a diversity problem that exists elsewhere: the number of female core developers for CPython still stands at a grand total of zero, and the number of female patch contributors over the life of the projects is incredibly low as well (as indicated by the CPython ACKS file.
Other significant Python communities (including the PSF itself) are better in this regard than CPython core development, but a policy (personal or otherwise) that would make panels on CPython verboten is clearly either premature or lacking in nuance.