Add note about cURL error 52 with CrateDB Cloud

docs/connect.rst

@@ -99,6 +99,16 @@ You can get a PDO connection like this:
    authenticate as the CrateDB superuser, which is ``crate``. The superuser
    does not have a password, so you should omit the ``password`` argument.
 
+CrateDB Cloud
+=================
+
+If you are connecting to CrateDB Cloud you will need to enable the SSL mode 
+by setting the connection's ``CRATE_ATTR_SSL_MODE`` attribute. 
+See the section below for details on how to do this.
+
+If this is not configured you will see the following error message: 
+``cURL error 52: Empty reply from server``
+
 Advanced settings
 =================