gpgme: Allow setuptools3-base to be excluded from the inherit list

Inheriting setuptools3-base adds a runtime dependency on Python.

This change makes inheriting setuptools3-base optional. If one does not want
a runtime dependency on Python, they can remove python from LANGUAGES.

Additionally, as Python 2 has been EOL for nearly 3 years now, all Python 2 related parts have been taken out.

Signed-off-by: David Bagonyi <david.bagonyi@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>