core: properly report 502 errors for gevent and gunicorn.

- gevent+gunicorn doesn't raise normal pycurl errors

rhodecode/lib/exceptions.py

@@ -132,6 +132,7 b' class VCSServerUnavailable(HTTPBadGatewa'
         'Incorrect vcs.server=host:port',
         'Incorrect vcs.server.protocol',
     ]
+
     def __init__(self, message=''):
         self.explanation = 'Could not connect to VCS Server'
         if message:

rhodecode/lib/vcs/client_http.py

@@ -197,6 +197,13 b' def _remote_call(url, payload, exception'
         response = session.post(url, data=msgpack.packb(payload))
     except pycurl.error as e:
         raise exceptions.HttpVCSCommunicationError(e)
+    except Exception as e:
+        message = getattr(e, 'message', '')
+        if 'Failed to connect' in message:
+            # gevent doesn't return proper pycurl errors
+            raise exceptions.HttpVCSCommunicationError(e)
+        else:
+            raise
 
     if response.status_code >= 400:
         log.error('Call to %s returned non 200 HTTP code: %s',