title: NoSuchModuleError: Can't load plugin: sqlalchemy.dialects:redshift.psycopg2
body: <p>I am trying to connect to redshift from my python code.
  my pip installed:</p>
  
  <pre><code>psycopg2==2.6.1
  redshift-sqlalchemy==0.4.1
  SQLAlchemy==1.0.9
  </code></pre>
  
  <p>and my virtual machine has:</p>
  
  <pre><code>libpq-dev
  python-psycopg2
  </code></pre>
  
  <p>But I am still getting </p>
  
  <pre><code> engine = create_engine('redshift+psycopg2://{}:{}@{}'.format(username, password, url))
    File "/opt/project/env/local/lib/python2.7/site-packages/sqlalchemy/engine/__init__.py", line 386, in create_engine
      return strategy.create(*args, **kwargs)
    File "/opt/project/env/local/lib/python2.7/site-packages/sqlalchemy/engine/strategies.py", line 51, in create
      entrypoint = u._get_entrypoint()
    File "/opt/project/env/local/lib/python2.7/site-packages/sqlalchemy/engine/url.py", line 131, in _get_entrypoint
      cls = registry.load(name)
    File "/opt/project/env/local/lib/python2.7/site-packages/sqlalchemy/util/langhelpers.py", line 205, in load
      (self.group, name))
  NoSuchModuleError: Can't load plugin: sqlalchemy.dialects:redshift.psycopg2
  </code></pre>
  
  <p>With the same config, I am able to run from my laptop (mac), but on linux, I guess some packages still missing? Any suggestion will be appreciated, thanks!</p>