logging: better message for HTTP status != 200

We already extract error message from Solr responses and that is
great. Unfortunately it can contain the data that may change with
every request (like document id).

This creates an issue when user uses Sentry or other solution
that captures logging or exceptions. Previous implementation
causes many duplicated events in Sentry if message extracted
using `self._extract_error(resp)` contained such variable data.

This change uses 'non-mutable' message that is complemented
with extracted data that using string formatting option supplied
by Python logging. Thanks to this, Sentry and other solutions
can perform better grouping of loging messages (by status code).

This is approach that is already used in handling other errors.

Author: acdha

AUTHORS

@@ -33,3 +33,4 @@ Contributors:
 * Karol Sikora (@sicarrots) for Solr 4 softCommit support
 * Çağatay Çallı (@faraday) for Solr 4 field update support
 * Emmanuel Leblond (@touilleMan) for fixing error handling on Python 3
+* Michał Jaworski (@swistakm) for improved Sentry-friendly logging

pysolr.py

@@ -386,10 +386,12 @@ def _send_request(self, method, path='', body=None, headers=None, files=None):
                       url, method, log_body[:10], end_time - start_time)
 
         if int(resp.status_code) != 200:
-            error_message = self._extract_error(resp)
-            self.log.error(error_message, extra={'data': {'headers': resp.headers,
-                                                          'response': resp.content}})
-            raise SolrError(error_message)
+            error_message = "Solr responded with an error (HTTP %s): %s"
+            solr_message = self._extract_error(resp)
+            self.log.error(error_message, resp.status_code, solr_message,
+                           extra={'data': {'headers': resp.headers,
+                                           'response': resp.content}})
+            raise SolrError(error_message % (resp.status_code, solr_message))
 
         return force_unicode(resp.content)