title: psycopg2 executemany not working
body: <p>If I run</p>
  
  <pre><code>cur.execute('SELECT * FROM some_table WHERE some_column = %s;', ('some_value',))
  </code></pre>
  
  <p>then a call to <code>cur.fetchall()</code> immediately afterwards succeeds, and produces an output that is entirely consistent with the result I get if I run the following in <code>psql</code>:</p>
  
  <pre><code>some_db=&gt; SELECT * FROM some_table WHERE some_column = 'some_value';
  </code></pre>
  
  <p>But if I run</p>
  
  <pre><code>cur.executemany('SELECT * FROM some_table WHERE some_column = %s;',
                  [('some_value',)])
  </code></pre>
  
  <p>...which should be basically equivalent to the <code>cur.execute(...)</code> statement before, the subsequent call to <code>cur.fetchall()</code> <strong>raises an exception</strong>:</p>
  
  <pre><code>ProgrammingError: no results to fetch
  </code></pre>
  
  <p>I get the same exception if the sequence passed as second argument in the call to <code>executemany</code> has multiple entries:</p>
  
  <pre><code>cur.executemany('SELECT * FROM some_table WHERE some_column = %s;',
                  [('some_value',), ('some_other_value',)])
  </code></pre>
  
  <p>...or if I use the <code>pyformat</code> style for passing parameters</p>
  
  <pre><code>cur.executemany('SELECT * FROM some_table WHERE some_column = %(v)s;',
                  [{'v': 'some_value'}, {'v': 'some_other_value'}])
  </code></pre>
  
  <p>What's wrong with my code?</p>
  
  <p>BTW, I'm aware of this <a href="https://stackoverflow.com/q/19154324/559827">earlier question</a>, but the answers there do not help.</p>