With fonttools installed in your Python (virtualenv, pipenv, etc):
$ python
>>> from fontTools.ttLib import TTFont
>>> f = TTFont('path/to/your/file.otf')
>>> f.flavor='woff2'
>>> f.save('path/to/your/file.woff2')
NOTE: you might need to install other fontTools dependencies ('brotli', others) to allow saving with flavor=woff2 to work correctly.