On a current seafile install, I go to

System Admin => Libraries

and then for any library open the Share dialog.

In the search field, I can enter a username or email to search for a user to share the library with, but I always get a 'Loading failed' error.
The corresponding error in seahub.log is:

2019-02-25 17:35:06,946 [ERROR] django.request:135 handle_uncaught_exception Internal Server Error: /api2/search-user/
Traceback (most recent call last):
 File "/usr/local/lib/python2.7/site-packages/django/core/handlers/exception.py", line 41, in inner
   response = get_response(request)
 File "/usr/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 249, in _legacy_get_response
   response = self._get_response(request)
 File "/usr/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 187, in _get_response
   response = self.process_exception_by_middleware(e, request)
 File "/usr/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 185, in _get_response
   response = wrapped_callback(request, *callback_args, **callback_kwargs)
 File "/usr/local/lib/python2.7/site-packages/django/views/decorators/csrf.py", line 58, in wrapped_view
   return view_func(*args, **kwargs)
 File "/usr/local/lib/python2.7/site-packages/django/views/generic/base.py", line 68, in view
   return self.dispatch(request, *args, **kwargs)
 File "/usr/local/lib/python2.7/site-packages/rest_framework/views.py", line 495, in dispatch
   response = self.handle_exception(exc)
 File "/usr/local/lib/python2.7/site-packages/rest_framework/views.py", line 455, in handle_exception
   self.raise_uncaught_exception(exc)
 File "/usr/local/lib/python2.7/site-packages/rest_framework/views.py", line 492, in dispatch
   response = handler(request, *args, **kwargs)
 File "/usr/local/www/haiwen/seafile-server/seahub/seahub/api2/endpoints/search_user.py", line 129, in get
   user_obj_list = ccnet_api.get_emailusers_in_list('DB', email_list_json) + \
AttributeError: 'CcnetAPI' object has no attribute 'get_emailusers_in_list'

The package versions are:

libsearpc-3.1.0,1
py27-seafdav-6.3.11
py27-seafobj-6.3.11
seafile-server-6.3.4_1
seahub-6.3.11


Now, I have an older installation still running

libsearpc-3.0.8_1,1
py27-seafdav-6.3.7
py27-seafobj-6.3.7
seafile-server-6.3.4_1
seahub-6.3.7_1

but otherwise the same config (webserver, seahub_settings, etc.) which does not show the issue.

Could this be a bug in the most recent version?