gatilegrid error message

[fitzlibutz]

gatilegrid requires Python '>=2.7, ~=3.5, ~=3.6, <4' but the running Python is 2.7.15

This is confusing to me. >=2.7 should work with 2.7.15?

Additonally this warning: "DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020. "
Changing PYTHON_CMD = $(VENV)/bin/python to python3 in the makefile seems to have no influence on the use of python2.

Sorry if this is a matter of false understanding; but I do not see where I can avoid the error message.

Thanks in advance for any hint,
Stefan

p.s.: I'm using ubuntu 18 in a virtualbox