run 'inv cov' just for Py2
run 'inv cov' just for Py2

lino-framework/book,lsaffre/lino_book,lino-framework/book,lino-framework/book,khchine5/book,khchine5/book,lino-framework/book,lsaffre/lino_book,lsaffre/lino_book,khchine5/book