Actually check connection errors

Fix issue #4463

CHANGELOG.md

@@ -47,6 +47,7 @@
 - [#4296](https://github.com/influxdb/influxdb/pull/4296): Reject line protocol ending with '-'. Fixes [#4272](https://github.com/influxdb/influxdb/issues/4272)
 - [#4333](https://github.com/influxdb/influxdb/pull/4333): Retry monitor storage creation and storage only on Leader.
 - [#4276](https://github.com/influxdb/influxdb/issues/4276): Walk DropSeriesStatement & check for empty sources
+- [#4465](https://github.com/influxdb/influxdb/pull/4465): Actually display a message if the CLI can't connect to the database.
 - [#4342](https://github.com/influxdb/influxdb/pull/4342): Fix mixing aggregates and math with non-aggregates. Thanks @kostya-sh.
 - [#4349](https://github.com/influxdb/influxdb/issues/4349): If HH can't unmarshal a block, skip that block.
 - [#4354](https://github.com/influxdb/influxdb/pull/4353): Fully lock node queues during hinted handoff. Fixes one cause of missing data on clusters.

cmd/influx/main.go

@@ -158,7 +158,10 @@ Examples:
 	}
 
 	if err := c.connect(""); err != nil {
-
+		fmt.Fprintf(os.Stderr,
+			"Failed to connect to %s\nPlease check your connection settings and ensure 'influxd' is running.\n",
+			c.Client.Addr())
+		return
 	}
 	if c.Execute == "" && !c.Import {
 		fmt.Printf("Connected to %s version %s\n", c.Client.Addr(), c.Version)