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

@@ -3,17 +3,17 @@
 
 from trytond.pool import Pool
 
-from .stock import *
-from .carrier import *
+from . import stock
+from . import carrier
 
 
 def register():
     Pool.register(
-        PackageType,
-        Package,
-        ShipmentOut,
-        Carrier,
+        stock.PackageType,
+        stock.Package,
+        stock.ShipmentOut,
+        carrier.Carrier,
         module='stock_package_shipping', type_='model')
     Pool.register(
-        CreateShipping,
+        stock.CreateShipping,
         module='stock_package_shipping', type_='wizard')

carrier.py

@@ -4,8 +4,6 @@
 from trytond.model import fields
 from trytond.pool import PoolMeta
 
-__all__ = ['Carrier']
-
 
 class Carrier(metaclass=PoolMeta):
     __name__ = 'carrier'

setup.py

@@ -80,8 +80,8 @@ setup(name=name,
     keywords='tryton stock package shipping',
     package_dir={'trytond.modules.stock_package_shipping': '.'},
     packages=(
-        ['trytond.modules.stock_package_shipping'] +
-        ['trytond.modules.stock_package_shipping.%s' % p
+        ['trytond.modules.stock_package_shipping']
+        + ['trytond.modules.stock_package_shipping.%s' % p
             for p in find_packages()]
         ),
     package_data={
@@ -96,7 +96,8 @@ 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 :: Czech',

stock.py

@@ -11,8 +11,6 @@ from trytond.wizard import Wizard, StateTransition
 
 from .exceptions import PackWarning
 
-__all__ = ['PackageType', 'Package', 'ShipmentOut', 'CreateShipping']
-
 
 class PackageType(metaclass=PoolMeta):
     __name__ = 'stock.package.type'