Help - pgAdmin4 fails with AttributeError: 'str' object has no attribute 'gettext'

[axelhuizinga]

Starting pgAdmin 4. Please navigate to http://127.0.0.1:5050 in your browser.
2018-03-25 19:41:11,128: ERROR werkzeug: Error on request:
Traceback (most recent call last):
File "/usr/local/lib/python2.7/dist-packages/werkzeug/serving.py", line 270, in run_wsgi
execute(self.server.app)
File "/usr/local/lib/python2.7/dist-packages/werkzeug/serving.py", line 258, in execute
application_iter = app(environ, start_response)
File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1997, in call
return self.wsgi_app(environ, start_response)
File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1985, in wsgi_app
response = self.handle_exception(e)
File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1540, in handle_exception
reraise(exc_type, exc_value, tb)
File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1982, in wsgi_app
response = self.full_dispatch_request()
File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1607, in full_dispatch_request
self.try_trigger_before_first_request_functions()
File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1654, in try_trigger_before_first_request_functions
func()
File "/usr/share/pgadmin4/web/pgadmin/utils/init.py", line 43, in create_module_preference
self.register_preferences()
File "/usr/share/pgadmin4/web/pgadmin/browser/init.py", line 208, in register_preferences
gettext("Show system objects?"), 'boolean', False,
File "/usr/local/lib/python2.7/dist-packages/flask_babelex/init.py", line 624, in gettext
return get_domain().gettext(*args, **kwargs)
AttributeError: 'str' object has no attribute 'gettext'

[TaaviE]

I'm getting the same error with a different project.