title: psycopg2 connect gives operational error unsupported frontend protocol
body: <p>I'm trying to connect to a postgres 12.2 database from anaconda python 3.8.2 on Windows 10. I am using a conda environment with the following packages installed:</p>
  
  <pre><code>asgiref==3.2.7
  certifi==2020.4.5.1
  Django==3.0.4
  django-crispy-forms==1.8.1
  Jinja2==2.11.1
  MarkupSafe==1.1.1
  psycopg2==2.8.5
  pytz==2019.3
  sqlparse==0.3.1
  wincertstore==0.2
  </code></pre>
  
  <p>I have created a database and I can connect using psql and pgAdmin. At the python prompt I can import psycopg2 but I get an error connecting to the database: </p>
  
  <pre><code>&gt;&gt;&gt; import psycopg2
  &gt;&gt;&gt; c = psycopg2.connect("host='localhost' dbname='mydb' user='myuser' password='secret'")
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
    File "J:\Programs\Anaconda3\envs\myenv\lib\site-packages\psycopg2\__init__.py", line 127, in connect
      conn = _connect(dsn, connection_factory=connection_factory, **kwasync)
  psycopg2.OperationalError: FATAL:  unsupported frontend protocol 1234.5679: server supports 2.0 to 3.0
  </code></pre>