Unexpected process exit while waiting for connection details from external dart_format.

Please supply any additional information here, e.g. the source code that caused the error:

```
StdErr: /Users/moali/.pub-cache/bin/dart_format: line 8: dart: command not found
Did you install the dart_format package?
Basically just execute this:<pre>dart pub global activate dart_format</pre>
```
```OS: Mac OS X
Plugin version: 2.0.32
External dart_format version: <unknown version>
```