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 .product import *
+from . import product
 
 
 def register():
     Pool.register(
-        Template,
-        Product,
-        ClassificationDummy,
-        ClassificationTreeDummy,
+        product.Template,
+        product.Product,
+        product.ClassificationDummy,
+        product.ClassificationTreeDummy,
         module='product_classification', type_='model')

product.py

@@ -5,9 +5,6 @@ from trytond.model import (ModelStorage, ModelView, DeactivableMixin, fields,
 from trytond.pool import PoolMeta, Pool
 from trytond.pyson import Eval
 
-__all__ = ['ClassificationMixin', 'classification_tree',
-    'Template', 'Product', 'ClassificationDummy', 'ClassificationTreeDummy']
-
 
 class ClassificationMixin(DeactivableMixin):
     __slots__ = ()

setup.py

@@ -78,8 +78,8 @@ setup(name=name,
     keywords='tryton product classification',
     package_dir={'trytond.modules.product_classification': '.'},
     packages=(
-        ['trytond.modules.product_classification'] +
-        ['trytond.modules.product_classification.%s' % p
+        ['trytond.modules.product_classification']
+        + ['trytond.modules.product_classification.%s' % p
             for p in find_packages()]
         ),
     package_data={
@@ -91,7 +91,8 @@ setup(name=name,
         'Environment :: Plugins',
         'Framework :: Tryton',
         'Intended Audience :: Developers',
-        '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)',

tests/__init__.py

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