Fix flake8 errors and warnings

We add the flake8 configuration used so we ensure everyone uses the same.
We remove the usage of __all__ for non public API.
When possible, we rationalize the class name according to its __name__ and module.

issue9082
review297061002

.flake8

@@ -0,0 +1,2 @@
+[flake8]
+ignore=E123,E124,E126,E128,W503

__init__.py

@@ -2,13 +2,13 @@
 # this repository contains the full copyright notices and license terms.
 
 from trytond.pool import Pool
-from .sale import *
+from . import sale
 
 
 def register():
     Pool.register(
-        SaleExtra,
-        SaleExtraLine,
-        Sale,
-        SaleLine,
+        sale.Extra,
+        sale.ExtraLine,
+        sale.Sale,
+        sale.Line,
         module='sale_extra', type_='model')

sale.py

@@ -12,9 +12,6 @@ from trytond.model import (
 from trytond.pyson import Eval, If
 from trytond.transaction import Transaction
 
-__all__ = ['Sale', 'SaleLine',
-    'SaleExtra', 'SaleExtraLine']
-
 
 class Sale(metaclass=PoolMeta):
     __name__ = 'sale.sale'
@@ -57,13 +54,13 @@ class Sale(metaclass=PoolMeta):
         self.lines = lines
 
 
-class SaleLine(metaclass=PoolMeta):
+class Line(metaclass=PoolMeta):
     __name__ = 'sale.line'
 
     extra = fields.Many2One('sale.extra.line', 'Extra', ondelete='RESTRICT')
 
 
-class SaleExtra(DeactivableMixin, ModelSQL, ModelView, MatchMixin):
+class Extra(DeactivableMixin, ModelSQL, ModelView, MatchMixin):
     'Sale Extra'
     __name__ = 'sale.extra'
 
@@ -114,7 +111,7 @@ class SaleExtra(DeactivableMixin, ModelSQL, ModelView, MatchMixin):
         sql_table = cls.__table__()
         price_list = PriceList.__table__()
 
-        super(SaleExtra, cls).__register__(module_name)
+        super().__register__(module_name)
 
         table = cls.__table_handler__(module_name)
         # Migration from 3.6: price_list not required and new company
@@ -189,7 +186,7 @@ class SaleExtra(DeactivableMixin, ModelSQL, ModelView, MatchMixin):
         pattern = pattern.copy()
         sale_amount = pattern.pop('sale_amount')
 
-        match = super(SaleExtra, self).match(pattern)
+        match = super().match(pattern)
 
         if self.sale_amount is not None:
             if sale_amount < self.sale_amount:
@@ -197,7 +194,7 @@ class SaleExtra(DeactivableMixin, ModelSQL, ModelView, MatchMixin):
         return match
 
 
-class SaleExtraLine(sequence_ordered(), ModelSQL, ModelView, MatchMixin):
+class ExtraLine(sequence_ordered(), ModelSQL, ModelView, MatchMixin):
     'Sale Extra Line'
     __name__ = 'sale.extra.line'
 
@@ -224,7 +221,7 @@ class SaleExtraLine(sequence_ordered(), ModelSQL, ModelView, MatchMixin):
 
     @classmethod
     def __setup__(cls):
-        super(SaleExtraLine, cls).__setup__()
+        super().__setup__()
         cls._order.insert(1, ('extra', 'ASC'))
 
     @fields.depends('product')
@@ -254,7 +251,7 @@ class SaleExtraLine(sequence_ordered(), ModelSQL, ModelView, MatchMixin):
         pattern = pattern.copy()
         sale_amount = pattern.pop('sale_amount')
 
-        match = super(SaleExtraLine, self).match(pattern)
+        match = super().match(pattern)
 
         if self.sale_amount is not None:
             if sale_amount < self.sale_amount:

setup.py

@@ -79,8 +79,8 @@ setup(name=name,
     keywords='tryton sale extra premium cost',
     package_dir={'trytond.modules.sale_extra': '.'},
     packages=(
-        ['trytond.modules.sale_extra'] +
-        ['trytond.modules.sale_extra.%s' % p for p in find_packages()]
+        ['trytond.modules.sale_extra']
+        + ['trytond.modules.sale_extra.%s' % p for p in find_packages()]
         ),
     package_data={
         'trytond.modules.sale_extra': (info.get('xml', [])
@@ -93,7 +93,8 @@ setup(name=name,
         'Intended Audience :: Developers',
         'Intended Audience :: Financial and Insurance Industry',
         'Intended Audience :: Legal Industry',
-        'License :: OSI Approved :: GNU General Public License v3 or later (GPLv3+)',
+        'License :: OSI Approved :: '
+        'GNU General Public License v3 or later (GPLv3+)',
         'Natural Language :: Bulgarian',
         'Natural Language :: Catalan',
         'Natural Language :: Chinese (Simplified)',