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

@@ -2,21 +2,21 @@
 # this repository contains the full copyright notices and license terms.
 
 from trytond.pool import Pool
-from .purchase_request import *
-from .purchase import *
-from .party import PartyReplace
+from . import purchase_request
+from . import purchase
+from . import party
 
 
 def register():
     Pool.register(
-        PurchaseRequest,
-        HandlePurchaseCancellationExceptionStart,
-        CreatePurchaseAskParty,
-        Purchase,
-        PurchaseLine,
+        purchase_request.PurchaseRequest,
+        purchase_request.HandlePurchaseCancellationExceptionStart,
+        purchase_request.CreatePurchaseAskParty,
+        purchase.Purchase,
+        purchase.Line,
         module='purchase_request', type_='model')
     Pool.register(
-        CreatePurchase,
-        HandlePurchaseCancellationException,
-        PartyReplace,
+        purchase_request.CreatePurchase,
+        purchase_request.HandlePurchaseCancellationException,
+        party.Replace,
         module='purchase_request', type_='wizard')

party.py

@@ -2,14 +2,12 @@
 # this repository contains the full copyright notices and license terms.
 from trytond.pool import PoolMeta
 
-__all__ = ['PartyReplace']
 
-
-class PartyReplace(metaclass=PoolMeta):
+class Replace(metaclass=PoolMeta):
     __name__ = 'party.replace'
 
     @classmethod
     def fields_to_replace(cls):
-        return super(PartyReplace, cls).fields_to_replace() + [
+        return super().fields_to_replace() + [
             ('purchase.request', 'party'),
             ]

purchase.py

@@ -11,8 +11,6 @@ from trytond.pyson import Eval
 
 from .exceptions import PurchaseWarehouseWarning
 
-__all__ = ['Purchase', 'PurchaseLine']
-
 
 def process_request(func):
     @wraps(func)
@@ -84,7 +82,7 @@ class Purchase(metaclass=PoolMeta):
         super(Purchase, cls).do(purchases)
 
 
-class PurchaseLine(metaclass=PoolMeta):
+class Line(metaclass=PoolMeta):
     __name__ = 'purchase.line'
 
     requests = fields.One2Many(
@@ -99,6 +97,6 @@ class PurchaseLine(metaclass=PoolMeta):
         Request = pool.get('purchase.request')
         with Transaction().set_context(_check_access=False):
             requests = [r for l in cls.browse(lines) for r in l.requests]
-        super(PurchaseLine, cls).delete(lines)
+        super().delete(lines)
         with Transaction().set_context(_check_access=False):
             Request.update_state(requests)

purchase_request.py

@@ -13,12 +13,6 @@ from trytond.pyson import If, In, Eval, Bool
 from trytond.transaction import Transaction
 from trytond.pool import Pool
 
-__all__ = ['PurchaseRequest',
-    'CreatePurchaseAskParty', 'CreatePurchase',
-    'HandlePurchaseCancellationException',
-    'HandlePurchaseCancellationExceptionStart',
-    ]
-
 STATES = {
     'readonly': Eval('state') != 'draft',
     }

setup.py

@@ -80,8 +80,8 @@ setup(name=name,
     keywords='tryton purchase request',
     package_dir={'trytond.modules.purchase_request': '.'},
     packages=(
-        ['trytond.modules.purchase_request'] +
-        ['trytond.modules.purchase_request.%s' % p for p in find_packages()]
+        ['trytond.modules.purchase_request']
+        + ['trytond.modules.purchase_request.%s' % p for p in find_packages()]
         ),
     package_data={
         'trytond.modules.purchase_request': (info.get('xml', [])
@@ -95,7 +95,8 @@ 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)',