This should fix the tests, that are currently failing on CI with:
```
2022-07-05 16:19:13,250 259 INFO odoo odoo.service.server: Starting post tests
2022-07-05 16:19:13,253 259 ERROR odoo odoo.tests.loader: Can not `import mail_autosubscribe`.
Traceback (most recent call last):
File "/opt/odoo/odoo/tests/loader.py", line 33, in _get_tests_modules
mod = importlib.import_module('.tests', modpath)
File "/usr/lib/python3.8/importlib/__init__.py", line 127, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "<frozen importlib._bootstrap>", line 1014, in _gcd_import
File "<frozen importlib._bootstrap>", line 991, in _find_and_load
File "<frozen importlib._bootstrap>", line 975, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 671, in _load_unlocked
File "<frozen importlib._bootstrap_external>", line 848, in exec_module
File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
File "/__w/social/social/mail_autosubscribe/tests/__init__.py", line 1, in <module>
from . import test_mail_autosubscribe
File "/__w/social/social/mail_autosubscribe/tests/test_mail_autosubscribe.py", line 5, in <module>
from odoo_test_helper import FakeModelLoader
ModuleNotFoundError: No module named 'odoo_test_helper'
```
- FIX bug when split email message by `to_keep` parameter. When the html code is split, it is broken. As a result of this, when it use `fromstring`,
it try to fix this by closing tags.
Example about fixed functionality:
message:
`
<table>
<tr>
<td>
{to_keep}
</td>
</tr>
</table>
`
Split messsage inside `remove_href_odoo` function:
part[0]
`
<table>
<tr>
<td>
`
--------
part[1]
`
</td>
</tr>
</table>
`
-----------------
Result when join by `to_keep`
`
<table>
<tr>
<td>
{to_keep}
</td>
</tr>
</table>
`
