grafana_folder: Return better message if version cannot be retrieved

Ref: #147

plugins/modules/grafana_folder.py

@@ -162,6 +162,9 @@
 
 __metaclass__ = type
 
+class GrafanaError(Exception):
+    pass
+
 
 class GrafanaFolderInterface(object):
 
@@ -175,7 +178,10 @@ def __init__(self, module):
             self.headers["Authorization"] = basic_auth_header(module.params['url_username'], module.params['url_password'])
         # }}}
         self.grafana_url = module.params.get("url")
-        grafana_version = self.get_version()
+        try:
+            grafana_version = self.get_version()
+        except GrafanaError as e:
+            self._module.fail_json(failed=True, msg=to_text(e))
         if grafana_version["major"] < 5:
             self._module.fail_json(failed=True, msg="Folders API is available starting Grafana v5")
 
@@ -205,8 +211,10 @@ def get_version(self):
         url = "/api/health"
         response = self._send_request(url, data=None, headers=self.headers, method="GET")
         version = response.get("version")
-        major, minor, rev = version.split(".")
-        return {"major": int(major), "minor": int(minor), "rev": int(rev)}
+        if version is not None:
+            major, minor, rev = version.split(".")
+            return {"major": int(major), "minor": int(minor), "rev": int(rev)}
+        raise GrafanaError("Failed to retrieve version from '%s'" % url)
 
     def create_folder(self, title):
         url = "/api/folders"