title: GridSearchCV and LogisticRegression raise ValueError: Can't handle mix of continuous and binary
body: <p>I'm trying to run gridsearch with LogisticRegression, and get </p>
  
  <pre><code>ValueError: Can't handle mix of continuous and binary
  </code></pre>
  
  <p>I've traced this error to <code>metrics.accuracy_score</code>. Apparently the prediction doesn't go so well, and while the y_true is continuous (as is the rest of the data), y_pred is all zeros and is thus classified as binary.</p>
  
  <ul>
  <li>Is there any way to avoid this error? </li>
  <li>Does the nature of y_pred means I have no business using logistic regression at all, or could this be a result of the parameters used?</li>
  </ul>
  
  <p>Thanks</p>