Sqlalchemy / psycopg2 error when trying to connect to postgres

I am spinning up redash using helm on GKE with master/node version 1.12.10-gke.17 and istio 1.1.15
I use as database a GCP CloudSQL with postgres 9.6

When trying to execute the create_db script from the redash image (7.0.0.b18042) I encounter the following error

 Traceback (most recent call last):
   File "/app/manage.py", line 9, in <module>
     manager()
   File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 716, in __call__
     return self.main(*args, **kwargs)
   File "/usr/local/lib/python2.7/dist-packages/flask/cli.py", line 345, in main
     return AppGroup.main(self, *args, **kwargs)
   File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 696, in main
     rv = self.invoke(ctx)
   File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 1060, in invoke
     return _process_result(sub_ctx.command.invoke(sub_ctx))
   File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 1060, in invoke
     return _process_result(sub_ctx.command.invoke(sub_ctx))
   File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 889, in invoke
     return ctx.invoke(self.callback, **ctx.params)
   File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 534, in invoke
     return callback(*args, **kwargs)
   File "/usr/local/lib/python2.7/dist-packages/click/decorators.py", line 17, in new_func
     return f(get_current_context(), *args, **kwargs)
   File "/usr/local/lib/python2.7/dist-packages/flask/cli.py", line 229, in decorator
     return __ctx.invoke(f, *args, **kwargs)
   File "/usr/local/lib/python2.7/dist-packages/click/core.py", line 534, in invoke
     return callback(*args, **kwargs)
   File "/app/redash/cli/database.py", line 31, in create_tables
     db.create_all()
   File "/usr/local/lib/python2.7/dist-packages/flask_sqlalchemy/__init__.py", line 963, in create_all
     self._execute_for_all_tables(app, bind, 'create_all')
   File "/usr/local/lib/python2.7/dist-packages/flask_sqlalchemy/__init__.py", line 955, in _execute_for_all_tables
     op(bind=self.get_engine(app, bind), **extra)
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/sql/schema.py", line 4005, in create_all
     tables=tables)
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 1939, in _run_visitor
     with self._optional_conn_ctx_manager(connection) as conn:
   File "/usr/lib/python2.7/contextlib.py", line 17, in __enter__
     return self.gen.next()
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 1932, in _optional_conn_ctx_manager
     with self.contextual_connect() as conn:
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 2123, in contextual_connect
     self._wrap_pool_connect(self.pool.connect, None),
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 2162, in _wrap_pool_connect
     e, dialect, self)
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 1476, in _handle_dbapi_exception_noconnection
     exc_info
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/util/compat.py", line 265, in raise_from_cause
     reraise(type(exception), exception, tb=exc_tb, cause=cause)
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 2158, in _wrap_pool_connect
     return fn()
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 400, in connect
     return _ConnectionFairy._checkout(self)
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 788, in _checkout
     fairy = _ConnectionRecord.checkout(pool)
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 529, in checkout
     rec = pool._do_get()
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 1193, in _do_get
     self._dec_overflow()
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/util/langhelpers.py", line 66, in __exit__
     compat.reraise(exc_type, exc_value, exc_tb)
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 1190, in _do_get
     return self._create_connection()
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 347, in _create_connection
     return _ConnectionRecord(self)
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 474, in __init__
     self.__connect(first_connect_check=True)
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/pool.py", line 671, in __connect
     connection = pool._invoke_creator(self)
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/strategies.py", line 106, in connect
     return dialect.connect(*cargs, **cparams)
   File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/default.py", line 412, in connect
     return self.dbapi.connect(*cargs, **cparams)
   File "/usr/local/lib/python2.7/dist-packages/psycopg2/__init__.py", line 130, in connect
     conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
 sqlalchemy.exc.OperationalError: (psycopg2.OperationalError) server closed the connection unexpectedly
 	This probably means the server terminated abnormally
 	before or while processing the request.
  (Background on this error at: http://sqlalche.me/e/e3q8)

Any suggestions?

edit:

The same error (with smaller stack trace) is reproduced when I exec into a container and try to manually connect to CloudSQL

>>> import psycopg2
>>> conn = psycopg2.connect(host="192.44.33.1",database="postgres", user="postgres", password="mypass")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/psycopg2/__init__.py", line 130, in connect
    conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
psycopg2.OperationalError: server closed the connection unexpectedly
	This probably means the server terminated abnormally
	before or while processing the request.