Warn user when kaggle.json not found

If kaggle.json is not found and the credentials were also not set in the environment, raise an error showing the expected location of kaggle.json

Author: Conengmo

kaggle/api/kaggle_api_extended.py

@@ -99,13 +99,17 @@ def authenticate(self):
 
         config_data = {}
 
-        # Step 1: read in configuration file, if it exists
-        if os.path.exists(self.config):
-            config_data = self.read_config_file(config_data)
-
-        # Step 2:, get username/password from environment
+        # Step 1: try getting username/password from environment
         config_data = self.read_config_environment(config_data)
 
+        # Step 2: if credentials were not in environment read in configuration file
+        if 'username' not in config_data or 'key' not in config_data:
+            if os.path.exists(self.config):
+                config_data = self.read_config_file(config_data)
+            else:
+                raise IOError('Could not find kaggle.json. Make sure it\'s located in {}.'
+                              ' Or use the environment method.'.format(self.config_dir))
+
         # Step 3: load into configuration!
         self._load_config(config_data)