Remove Python2 support

[a-detiste]

the six library is being slowly removed from distributions

[jenisys]

• Currently, I have a dependency that uses parse-type and still supports Python 2.7
• I remove Python 2.7 support in the next few months (but not now)

[a-detiste]

Thanks. I guess we are waiting on the same thing https://github.com/behave/behave/issues/855