[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.
option_group_changed('port', 'main', 'web')
option_group_changed('query-log-file', 'main', 'web')
option_group_changed('profile', 'main', 'web')
option_group_changed('max-post-length', 'main', 'web')