[FIX] packaging,doc: minimum python version is 3.6

In 12.0 it was 3.5 but for 13.0, it is acceptable 3.6.
Debian Buster has 3.7 and Ubuntu 18.04 LTS has 3.6
This will avoid undeterminist errors with OrderedDict

CentOS 7 still does not ship python3 by default but it is possible to
install it and CentOS 8 with python 3.6 was released in septembre 2019

closes odoo/odoo#38364

Signed-off-by: Martin Trigaux (mat) <mat@odoo.com>

doc/setup/install.rst

@@ -200,9 +200,7 @@ If you need this feature, you can install the python module like this:
 Fedora
 ''''''
 
-Odoo 13.0 'rpm' package supports Fedora 26.
-As of 2017, CentOS does not have the minimum Python requirements (3.5) for
-Odoo 13.0.
+Odoo 13.0 'rpm' package supports Fedora 30.
 
 Prepare
 ^^^^^^^
@@ -330,13 +328,13 @@ Prepare
 Python
 ^^^^^^
 
-Odoo requires Python 3.5 or later to run. Use the the official `Python 3 installer
+Odoo requires Python 3.6 or later to run. Use the the official `Python 3 installer
 <https://www.python.org/downloads/windows/>`_ to download and install Python 3 on your machine.
 
 During installation, check **Add Python 3 to PATH**, then click **Customize Installation** and make
 sure that **pip** is checked.
 
-.. note:: If Python 3 is already installed, make sure that it is 3.5 or above, as previous versions
+.. note:: If Python 3 is already installed, make sure that it is 3.6 or above, as previous versions
           are not compatible with Odoo.
 
           .. code-block:: doscon
@@ -490,10 +488,10 @@ Prepare
 Python
 ^^^^^^
 
-Odoo requires Python 3.5 or later to run. Use your package manager to download and install Python 3
+Odoo requires Python 3.6 or later to run. Use your package manager to download and install Python 3
 on your machine if it is not already done.
 
-.. note:: If Python 3 is already installed, make sure that it is 3.5 or above, as previous versions
+.. note:: If Python 3 is already installed, make sure that it is 3.6 or above, as previous versions
           are not compatible with Odoo.
 
           .. code-block:: console
@@ -646,10 +644,10 @@ Prepare
 Python
 ^^^^^^
 
-Odoo requires Python 3.5 or later to run. Use your preferred package manager (homebrew_, macports_)
+Odoo requires Python 3.6 or later to run. Use your preferred package manager (homebrew_, macports_)
 to download and install Python 3 on your machine if it is not already done.
 
-.. note:: If Python 3 is already installed, make sure that it is 3.5 or above, as previous versions
+.. note:: If Python 3 is already installed, make sure that it is 3.6 or above, as previous versions
           are not compatible with Odoo.
 
           .. code-block:: console

odoo/__init__.py

@@ -10,9 +10,8 @@
 #----------------------------------------------------------
 __path__ = __import__('pkgutil').extend_path(__path__, __name__)
 
-# As of version 12.0, python 2 is no longer supported, ensure py version is >= 3.5
 import sys
-assert sys.version_info > (3, 5), "Python 2 detected, Odoo requires Python >= 3.5 to run."
+assert sys.version_info > (3, 6), "Outdated python version detected, Odoo requires Python >= 3.6 to run."
 
 #----------------------------------------------------------
 # Running mode flags (gevent, prefork)

setup.py

@@ -57,7 +57,7 @@ setup(
         'xlsxwriter',
         'xlwt',
     ],
-    python_requires='>=3.5',
+    python_requires='>=3.6',
     extras_require={
         'ldap': ['pyldap'],
         'SSL': ['pyopenssl'],