[pkg] require python >= 3.4
This avoid pip pulling a version that does not run on python2 when using a
python2 environment.
Since we already released some 3.27 releases in pypi, I think we should release
3.27.3 and remove releases 3.27.2, 3.27.1 and 3.27.0 from pypi.
===================
Changelog history
===================
.. include:: 3.27.rst
.. include:: 3.26.rst
.. include:: 3.25.rst
.. include:: 3.24.rst
.. include:: 3.23.rst
.. include:: 3.22.rst
.. include:: 3.21.rst
.. include:: 3.20.rst
.. include:: 3.19.rst
.. include:: 3.18.rst
.. include:: 3.17.rst
.. include:: 3.16.rst
.. include:: 3.15.rst
.. include:: 3.14.rst