[FIX] mass_mailing: handle UnidentifiedImageError while convert image to url

Currently, a logger exception is generated when the user tries to upload
any image as document in the mass mail.

This is because an UnidentifiedImageError occurs when the user uploads
an image file as a document and code [1] tries to open it with Image.

This commit adds code that handles an UnidentifiedImageError, and it adds
the message in the log for an invalid image file.

[1] - https://github.com/odoo/odoo/blob/029b84f3c061f819bacb9a4818504cced4adeb1c/addons/mass_mailing/models/mailing.py#L1405

sentry-4311184876

closes odoo/odoo#159653

X-original-commit: e4b7ec191fc81ec806736758f273e20b6260bbeb
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>
Signed-off-by: ANSARI MAHAMADASIF (maan) <maan@odoo.com>

addons/mass_mailing/models/mailing.py

@@ -1440,6 +1440,9 @@ class MassMailing(models.Model):
                 )
 
             return content
+        except UnidentifiedImageError:
+            _logger.warning('This file could not be decoded as an image file.', exc_info=True)
+            raise
         except Exception as e:
             _logger.exception(e)
             raise ImportValidationError(_("Could not retrieve URL: %s", url)) from e