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

setup.py

@@ -83,8 +83,8 @@ setup(name=name,
     keywords='tryton account stock valuation continental',
     package_dir={'trytond.modules.account_stock_continental': '.'},
     packages=(
-        ['trytond.modules.account_stock_continental'] +
-        ['trytond.modules.account_stock_continental.%s' % p
+        ['trytond.modules.account_stock_continental']
+        + ['trytond.modules.account_stock_continental.%s' % p
             for p in find_packages()]
         ),
     package_data={
@@ -98,7 +98,8 @@ 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)',

stock.py

@@ -6,8 +6,6 @@ from trytond.model import Workflow, ModelView
 from trytond.pool import Pool, PoolMeta
 from trytond.transaction import Transaction
 
-__all__ = ['Move']
-
 
 class Move(metaclass=PoolMeta):
     __name__ = 'stock.move'
@@ -24,7 +22,8 @@ class Move(metaclass=PoolMeta):
             'wrong type'
 
         move_line = AccountMoveLine()
-        if ((type_.endswith('supplier')
+        if ((
+                    type_.endswith('supplier')
                     or type_ == 'in_production')
                 and self.product.cost_price_method != 'fixed'):
             with Transaction().set_context(date=self.effective_date):

tests/__init__.py

@@ -2,7 +2,7 @@
 # this repository contains the full copyright notices and license terms.
 
 try:
-    from trytond.modules.account_stock_continental.tests.test_account_stock_continental import suite
+    from trytond.modules.account_stock_continental.tests.test_account_stock_continental import suite  # noqa: E501
 except ImportError:
     from .test_account_stock_continental import suite