2.2.6

What's Changed

• [1.6] remove index-url to pypi.camptocamp.net by @jwkaltz in #3920
• 1.6 fix travis by @jwkaltz in #3934
• [doc] small precisions about update process by @jwkaltz in #3935
• small fix by @jwkaltz in #3944
• Merge remote-tracking branch 'origin/1.6' into 2.1 by @sbrunner in #3958
• Merge21 by @sbrunner in #3959
• Correctly return nillable for relations in md.xsd by @arnaud-morvan in #3951
• fix WFS access for QGIS3 clients (and others relying on metadata) by @jwkaltz in #4086
• Fix i18n dependencies by @jwkaltz in #4113
• Backport fix trigger on_role_name_change through alembic. by @arnaud-morvan in #4118
• Fix deep recursion detection in groups by @arnaud-morvan in #3880

Full Changelog: 2.2.5...2.2.6