change error handling in provisioning_proxy

gso/services/provisioning_proxy.py

@@ -35,10 +35,11 @@ def provision_node(
     }
 
     post_request = requests.post(
-        f'{pp_params.scheme}://{pp_params.api_base}'
-        f'/api/device',
+        f'{pp_params.scheme}://{pp_params.api_base}/api/device',
         json=parameters)
-    post_request.raise_for_status()
+
+    if post_request.status_code != 200:
+        raise AssertionError(post_request.text)
 
 
 @inputstep('Await provisioning proxy results', assignee=Assignee('SYSTEM'))