[IMP] Cleanup and refactoring of exception handling

Unify and refactor exception handling in framework and addons.

The generic `except_osv` is now deprecated, and replaced by more specialized exception subtypes:
 - `UserError` (renamed from Warning, as it conflicts with the built-in `Warning`) raised when a non-technical error occurs during a business operation. It could be a missing information in the data provided by the user, or a misconfiguration.
 - `AccessError`: raised when any operation is denied because the user conducting it does not have the required access rights.
 - `AccessDenied`: raised when an operation that requires authenticated access is attempted via an unauthenticated request.
 - `MissingError`: raised when an operation is attempted on a record that does not exist.
 - `ValidationError`: raised when an operation violates a SQL or Python constraint.
 - All other exceptions are internal errors due to a system problem or bug, and raised untouched to the client-side, which should display a traceback.

All exceptions take a single message argument.

The `test_exceptions` module has been updated to showcase both new and old (deprecated) exceptions.

A great many old `except_osv` had a useless title with "Error!" or "Warning", those have been removed, as this is handled by the client-side widget that displays the messages.

This commit introduces a more consistent policy for logging errors and warnings:
 - All messages that do not require administrator attention should be logged at INFO level or lower. This includes all errors that are notified to the user in a friendly manner, even for access right problems or validation errors during business operations.
 - All messages that indicate a likely misconfiguration or malicious use by the users should be logged at WARNING level, as they typically require administrator attention.
 - All other unhandled internal errors cannot typically be handled by the user and should be logged at ERROR or higher level, as they require immediate administrator attention.

1 files changed, 2 insertions, 3 deletions

diff --git a/addons/website_mail/models/mail_message.py b/addons/website_mail/models/mail_message.py
index edaa8c49a5d..3bd694b14d5 100644
--- a/addons/website_mail/models/mail_message.py
+++ b/addons/website_mail/models/mail_message.py
@@ -23,6 +23,7 @@ from openerp import SUPERUSER_ID
 from openerp.tools import html2plaintext
 from openerp.tools.translate import _
 from openerp.osv import osv, fields, expression
+from openerp.exceptions import AccessError
 
 class MailMessage(osv.Model):
     _inherit = 'mail.message'
@@ -83,8 +84,6 @@ class MailMessage(osv.Model):
             if group_user_id in [group.id for group in group_ids]:
                 cr.execute('SELECT id FROM "%s" WHERE website_published IS FALSE AND id = ANY (%%s)' % (self._table), (ids,))
                 if cr.fetchall():
-                    raise osv.except_osv(
-                        _('Access Denied'),
-                        _('The requested operation cannot be completed due to security restrictions. Please contact your system administrator.\n\n(Document type: %s, Operation: %s)') % (self._description, operation))
+                    raise AccessError(_('The requested operation cannot be completed due to security restrictions. Please contact your system administrator.\n\n(Document type: %s, Operation: %s)') % (self._description, operation))
         return super(MailMessage, self).check_access_rule(cr, uid, ids=ids, operation=operation, context=context)