AttributeError: module 'psycopg2' has no attribute 'extensions'

[PeterJCLaw]

I'm not sure what triggers it, but after running for some time a Jacquard webserver instance will start failing requests (HTTP 500) which involve a directory lookup with the a stack trace that ends with:

  File "/usr/lib/python3/dist-packages/sqlalchemy/dialects/postgresql/psycopg2.py", line 579, in dbapi
    import psycopg2
  File "/usr/lib/python3/dist-packages/psycopg2/__init__.py", line 67, in <module>
    import psycopg2.extensions as _ext
AttributeError: module 'psycopg2' has no attribute 'extensions'

Full stack trace

ERROR:waitress:Exception when serving /users/1422012
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/waitress/channel.py", line 338, in service
    task.service()
  File "/usr/lib/python3/dist-packages/waitress/task.py", line 169, in service
    self.execute()
  File "/usr/lib/python3/dist-packages/waitress/task.py", line 399, in execute
    app_iter = self.channel.server.application(env, start_response)
  File "/usr/lib/python3/dist-packages/jacquard/service/wsgi.py", line 48, in application
    response = endpoint.handle(**kwargs)
  File "/usr/lib/python3/dist-packages/jacquard/service/endpoints.py", line 42, in handle
    settings = get_settings(user, self.config.storage, self.config.directory)
  File "/usr/lib/python3/dist-packages/jacquard/config.py", line 88, in directory
    return self._thread_local_property("directory", self._open_directory)
  File "/usr/lib/python3/dist-packages/jacquard/config.py", line 54, in _thread_local_property
    setattr(self._thread_local, name, generator())
  File "/usr/lib/python3/dist-packages/jacquard/config.py", line 78, in _open_directory
    return open_directory(self, self.directory_settings["engine"], kwargs)
  File "/usr/lib/python3/dist-packages/jacquard/directory/utils.py", line 14, in open_directory
    return cls.from_configuration(config, kwargs)
  File "/usr/lib/python3/dist-packages/jacquard/directory/union.py", line 82, in from_configuration
    return cls(cls._construct_subdirectories_from_config(config, options))
  File "/usr/lib/python3/dist-packages/jacquard/directory/union.py", line 32, in __init__
    self._subdirectories = list(subdirectories)
  File "/usr/lib/python3/dist-packages/jacquard/directory/union.py", line 65, in _construct_subdirectories_from_config
    yield open_directory(config, engine, sub_configuration)
  File "/usr/lib/python3/dist-packages/jacquard/directory/utils.py", line 14, in open_directory
    return cls.from_configuration(config, kwargs)
  File "/usr/lib/python3/dist-packages/jacquard/directory/base.py", line 41, in from_configuration
    return cls(**options)
  File "/usr/lib/python3/dist-packages/jacquard/directory/django.py", line 40, in __init__
    self.engine = sqlalchemy.create_engine(url)
  File "/usr/lib/python3/dist-packages/sqlalchemy/engine/__init__.py", line 386, in create_engine
    return strategy.create(*args, **kwargs)
  File "/usr/lib/python3/dist-packages/sqlalchemy/engine/strategies.py", line 75, in create
    dbapi = dialect_cls.dbapi(**dbapi_args)
  File "/usr/lib/python3/dist-packages/sqlalchemy/dialects/postgresql/psycopg2.py", line 579, in dbapi
    import psycopg2
  File "/usr/lib/python3/dist-packages/psycopg2/__init__.py", line 67, in 
    import psycopg2.extensions as _ext
AttributeError: module 'psycopg2' has no attribute 'extensions'

The odd part is that the Jacquard instance does work to start with. Running import psycopg2 in a python3 shell on the same machine also works fine.

We do have a plugin in /etc/jacquard/plugins/, but not called psycopg2.