Improve error message when MQTT error occures

conf/glances.conf

@@ -547,7 +547,7 @@ queue=glances_queue
 # Configuration for the --export mqtt option
 host=localhost
 port=1883
-tls=true
+tls=false
 user=guest
 password=guest
 topic=glances

glances/exports/glances_mqtt.py

@@ -45,7 +45,6 @@ class Export(GlancesExport):
 
         # Get the current hostname
         self.hostname = socket.gethostname()
-
         self.port = int(self.port) or 8883
         self.topic = self.topic or 'glances'
         self.user = self.user or 'glances'
@@ -59,7 +58,7 @@ class Export(GlancesExport):
         # Init the MQTT client
         self.client = self.init()
         if not self.client:
-            exit('MQTT client initialization failed')
+            exit("MQTT client initialization failed")
 
     def init(self):
         """Init the connection to the MQTT server."""
@@ -74,7 +73,7 @@ class Export(GlancesExport):
             client.loop_start()
             return client
         except Exception as e:
-            logger.critical("Connection to MQTT server failed : %s " % e)
+            logger.critical("Connection to MQTT server %s:%s failed with error: %s " % (self.host, self.port, e))
             return None
 
     def export(self, name, columns, points):