Improve error message when no device selected on post

Spent way too long debugging why a fresh install allowed "search" command to work, but not "copy". Turns out I had forgotten to run "config" first. The confusing part is that "search" seems to implicitly select a device while "copy" does not. Either way, using __get_uri() avoids some copy/paste URI generation and presents a better error message ("No device selected.") that would've been useful for initial debugging.

Author: pvulgaris

tablo/endpoint.py

@@ -96,9 +96,7 @@ def getCached(self, **kwargs):
     @request_handler
     def post(self, *args, **kwargs):
         return requests.post(
-            'http://{0}/{1}'.format(
-                self.device.address(), '/'.join(self.segments)
-            ),
+            self.__get_uri(),
             headers={'User-Agent': USER_AGENT},
             data=json.dumps(args and args[0] or kwargs)
         )