[IMP] packaging: remove some packages dependencies

On Ubuntu Xenian, the Odoo package was difficult to install because
three Debian packages were required but could not be found in Ubuntu
repositories. As those packages are not really crucial, they are
now only suggegsted by the Debian package which is therefore
installable on Ubuntu Xenial. One can manually install them as
explained in the documentation.

Closes #20000

debian/control

@@ -39,15 +39,17 @@ Depends:
  python3-suds,
  python3-tz,
  python3-vatnumber,
- python3-vobject,
  python3-werkzeug,
  python3-xlsxwriter,
  python3-yaml,
 Conflicts: tinyerp-server, openerp-server, openerp-web, openerp
 Replaces: tinyerp-server, openerp-server, openerp-web, openerp
 Recommends:
+ ${python3:Recommends},
  postgresql,
- python-gevent,
+ python3-pyldap,
+ python3-qrcode,
+ python3-vobject,
 Description: Open Source Apps To Grow Your Business
  Odoo, formerly known as OpenERP, is a suite of open-source business apps
  written in Python and released under the LGPLv3 license. This suite of

debian/py3dist-overrides

@@ -0,0 +1,3 @@
+pyldap
+vobject
+qrcode

doc/setup/install.rst

@@ -177,6 +177,22 @@ Or ``dpkg`` (handles less dependencies automatically):
     # dpkg -i <path_to_installation_package>
 
 
+.. warning:: The 3 following python packages are only suggested by the Debian package.
+             Those packages are not available in Ubuntu Xenial (16.04).
+
+* python3-vobject: Used in calendars to produce ical files.
+* python3-pyldap: Used to authenticat users with LDAP.
+* python3-qrcode: Used by the hardware driver for ESC/POS
+
+If you need one or all of the packages mentioned in the above warning, you can install them manually.
+One way to do it, is simply using pip3 like this:
+
+.. code-block:: console
+
+    $ sudo pip3 install vobject qrcode
+    $ sudo apt install libldap2-dev libsasl2-dev
+    $ sudo pip3 install pyldap
+
 This will install Odoo as a service, create the necessary PostgreSQL_ user
 and automatically start the server.