Backported updated RESTConnection.

main.py

@@ -15,7 +15,7 @@ class RestApp(App):
 
     def load_locations(self):
         self.root.ids.results.clear_widgets()
-        self.openmrs_connection.send_request('location', {}, None, self.on_locations_loaded,
+        self.openmrs_connection.send_request('location', None, None, self.on_locations_loaded,
                                              self.on_locations_not_loaded, self.on_locations_not_loaded)
 
     def on_locations_loaded(self, _, response):

openmrs.py

@@ -8,26 +8,27 @@ except ImportError:
     from urllib.parse import quote
 
 
-class RESTConnection(object):
-    @staticmethod
-    def _construct_url(authority, port, resource):
-        return 'http://{authority}:{port}/openmrs/ws/rest/v1/{resource}' \
-            .format(authority=authority, port=port, resource=resource)
-
+class RESTConnection:
     def __init__(self, authority, port, username, password):
         self.authority = authority
         self.port = port
-        credentials = '{username}:{password}'.format(username=username, password=password)
+        credentials = f'{username}:{password}'
         credentials = base64.standard_b64encode(credentials.encode('UTF8')).decode('UTF8')
         self.headers = {
-            'Authorization': 'Basic {credentials}'.format(credentials=credentials),
+            'Authorization': f'Basic {credentials}',
             'Content-type': 'application/json',
         }
 
+    def construct_url(self, resource, get_parameters=None):
+        get_parameters = '&'.join(f'{quote(str(key))}={quote(str(value))}' for key, value in get_parameters.items()) \
+            if get_parameters is not None else ''
+        return f'http://{self.authority}:{self.port}/openmrs/ws/rest/v1/{resource}?{get_parameters}'
+
+    def send_request_by_url(self, url, post_parameters, on_success, on_failure, on_error):
+        UrlRequest(url, req_headers=self.headers,
+                   req_body=json.dumps(post_parameters) if post_parameters is not None else None,
+                   on_success=on_success, on_failure=on_failure, on_error=on_error)
+
     def send_request(self, resource, get_parameters, post_parameters, on_success, on_failure, on_error):
-        url = RESTConnection._construct_url(self.authority, self.port, resource)
-        get_parameters = '&'.join('{key}={value}'.format(key=quote(key), value=quote(value))
-                                  for key, value in get_parameters.items()) if get_parameters is not None else ''
-        post_parameters = json.dumps(post_parameters) if post_parameters is not None else None
-        UrlRequest('{url}?{get_parameters}'.format(url=url, get_parameters=get_parameters), req_headers=self.headers,
-                   req_body=post_parameters, on_success=on_success, on_failure=on_failure, on_error=on_error)
+        url = self.construct_url(resource, get_parameters)
+        self.send_request_by_url(url, post_parameters, on_success, on_failure, on_error)