scm_app: add more debug info when unhandled errors happen on vcsserver.

rhodecode/lib/hooks_daemon.py

@@ -245,7 +245,6 b' def prepare_callback_daemon(extras, prot'
 
     # register txn_id
     extras['txn_id'] = txn_id
-
     log.debug('Prepared a callback daemon: %s at url `%s`',
               callback_daemon.__class__.__name__, callback_daemon.hooks_uri)
     return callback_daemon, extras
@@ -292,6 +291,9 b' class Hooks(object):'
 
         try:
             result = hook(extras)
+            if result is None:
+                raise Exception(
+                    'Failed to obtain hook result from func: {}'.format(hook))
         except HTTPBranchProtected as handled_error:
             # Those special cases doesn't need error reporting. It's a case of
             # locked repo or protected branch

rhodecode/lib/middleware/utils/scm_app_http.py

@@ -114,13 +114,17 b' class VcsHttpProxy(object):'
             stream=True)
 
         log.debug('http-app: got vcsserver response: %s', response)
+        if response.status_code >= 500:
+            log.error('Exception returned by vcsserver at: %s %s, %s',
+                      url, response.status_code, response.content)
+
         # Preserve the headers of the response, except hop_by_hop ones
         response_headers = [
             (h, v) for h, v in response.headers.items()
             if not wsgiref.util.is_hop_by_hop(h)
         ]
 
-        # Build status argument for start_reponse callable.
+        # Build status argument for start_response callable.
         status = '{status_code} {reason_phrase}'.format(
             status_code=response.status_code,
             reason_phrase=response.reason)