snapcraft 3.9.5 fails on launchpad builders

snapcraft is failing in the launchpad builders:

snapcraft 3.9.5 from Canonical* installed
/usr/lib/python2.7/dist-packages/pylxd/model.py:116: UserWarning: Attempted to set unknown attribute "description" on instance of "Container"
  key, self.__class__.__name__
Running repo phase...
Cloning into 'modem-manager'...
[15/Jan/2020:11:24:10 +0000] "CONNECT git.launchpad.net:443 HTTP/1.1" 200 15396260 "-" "git/2.17.1"
Running pull phase...
Sorry, an error occurred in Snapcraft:
'str' object has no attribute 'get'
Traceback (most recent call last):
  File "/snap/snapcraft/3914/bin/snapcraft", line 11, in <module>
    load_entry_point('snapcraft==3.9.1', 'console_scripts', 'snapcraft')()
  File "/snap/snapcraft/3914/lib/python3.6/site-packages/click/core.py", line 764, in __call__
    return self.main(*args, **kwargs)
  File "/snap/snapcraft/3914/lib/python3.6/site-packages/click/core.py", line 717, in main
    rv = self.invoke(ctx)
  File "/snap/snapcraft/3914/lib/python3.6/site-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/snap/snapcraft/3914/lib/python3.6/site-packages/snapcraft/cli/_command.py", line 87, in invoke
    return super().invoke(ctx)
  File "/snap/snapcraft/3914/lib/python3.6/site-packages/click/core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/snap/snapcraft/3914/lib/python3.6/site-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/snap/snapcraft/3914/lib/python3.6/site-packages/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/snap/snapcraft/3914/lib/python3.6/site-packages/snapcraft/cli/lifecycle.py", line 177, in pull
    _execute(steps.PULL, parts, **kwargs)
  File "/snap/snapcraft/3914/lib/python3.6/site-packages/snapcraft/cli/lifecycle.py", line 65, in _execute
    project_config = project_loader.load_config(project)
  File "/snap/snapcraft/3914/lib/python3.6/site-packages/snapcraft/internal/project_loader/__init__.py", line 39, in load_config
    return Config(project)
  File "/snap/snapcraft/3914/lib/python3.6/site-packages/snapcraft/internal/project_loader/_config.py", line 233, in __init__
    project._snap_meta = Snap.from_dict(self.data)
  File "/snap/snapcraft/3914/lib/python3.6/site-packages/snapcraft/internal/meta/snap.py", line 190, in from_dict
    slot = Slot.from_dict(slot_dict=slot_dict, slot_name=slot_name)
  File "/snap/snapcraft/3914/lib/python3.6/site-packages/snapcraft/internal/meta/slots.py", line 59, in from_dict
    interface = slot_dict.get("interface", slot_name)
AttributeError: 'str' object has no attribute 'get'

This is happening since 3.9.5 was released to stable.
See the full log in https://launchpadlibrarian.net/460693389/buildlog_snap_ubuntu_bionic_amd64_modem-manager-1.10-daily_BUILDING.txt.gz