VHM mappings can't be set

[thet]

I have a Plone 5.2 site installed on top of Zope 4.1.1 / Python 3.7

Setting a VHM map in http://localhost:8080/virtual_hosting/manage_edit like l1/Plone leads to this error:

2019-10-03 09:57:43,956 ERROR   [Zope.SiteErrorLog:18][waitress] 1570089463.9533460.9165882821177458 http://localhost:8080/virtual_hosting/set_map
Traceback (innermost last):
  Module ZPublisher.WSGIPublisher, line 155, in transaction_pubevents
  Module ZPublisher.WSGIPublisher, line 337, in publish_module
  Module ZPublisher.WSGIPublisher, line 255, in publish
  Module ZPublisher.mapply, line 85, in mapply
  Module Products.PDBDebugMode.wsgi_runcall, line 60, in pdb_runcall
  Module Products.SiteAccess.VirtualHostMonster, line 107, in set_map
TypeError: catching classes that do not inherit from BaseException is not allowed

It's because of the 'LineError' which is not a real exception and I couldn't find any information about.

This is just the error with the catching branch. The real error happens earlier in Products/SiteAccess/VirtualHostMonster:

  69                     pp = filter(None, path.split('/'))                                                                                                                                                                                   
  70                     if pp:                                                                                                                                                                                                               
  71  ->                     obpath = pp[:]          
TypeError: 'filter' object is not subscriptable
(Pdb++) pp
<filter object at 0x7f3a442e4550>
(Pdb++) list(pp)
['Plone2']