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

proteus/__init__.py

@@ -785,8 +785,8 @@ class Model(object):
 
     def __eq__(self, other):
         if isinstance(other, Model):
-            return ((self.__class__.__name__, self.id) ==
-                (other.__class__.__name__, other.id))
+            return ((self.__class__.__name__, self.id)
+                == (other.__class__.__name__, other.id))
         return NotImplemented
 
     def __ne__(self, other):

proteus/tests/__init__.py

@@ -10,7 +10,8 @@ import proteus.config
 
 os.environ.setdefault('TRYTOND_DATABASE_URI', 'sqlite:///:memory:')
 os.environ.setdefault('DB_NAME', ':memory:')
-from trytond.tests.test_tryton import doctest_setup, doctest_teardown
+from trytond.tests.test_tryton import (
+    doctest_setup, doctest_teardown)  # noqa: E402
 
 here = os.path.dirname(__file__)
 readme = os.path.normpath(os.path.join(here, '..', '..', 'README'))
@@ -46,6 +47,7 @@ def main():
     runner = unittest.TextTestRunner()
     return runner.run(suite)
 
+
 if __name__ == '__main__':
     sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.dirname(
         os.path.abspath(__file__)))))