Improve error handling with config file

.gitignore

@@ -1,3 +1,3 @@
-config.json
 .project
 .pydevproject
+PDMameUpdate.json

PDMameUpdate.py

@@ -33,12 +33,12 @@ Notes
     a cookies.txt file in the .config/transmission directory
     See: https://forum.transmissionbt.com/viewtopic.php?t=7468
 
-/!\/!\/!\/!\/!\/!\/!\/!\/!\/!\/!\/!\/!\/!\/!\/!\
-/!\ Provided with no warranty whatsoever.    /!\
-/!\ Make sure you understand what the script /!\
-/!\ does and adapt it to your context        /!\
-/!\ Use with caution.                        /!\
-/!\/!\/!\/!\/!\/!\/!\/!\/!\/!\/!\/!\/!\/!\/!\/!\
+!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
+!!! Provided with no warranty whatsoever.    !!!
+!!! Make sure you understand what the script !!!
+!!! does and adapt it to your context        !!!
+!!! Use with caution.                        !!!
+!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 '''
 import argparse
 import feedparser
@@ -59,17 +59,41 @@ from urllib.parse import quote
 def open_config_file():
     """Reads configuration from PDMameUpdate.json file"""
 
-    for loc in os.environ.get("PDMAMEUPDATE_CONF"), "/etc", os.path.expanduser("~"), os.curdir:
+    locations = (
+        os.environ.get("PDMAMEUPDATE_CONF"),
+        "/etc",
+        os.path.expanduser("~"),
+        os.curdir
+    )
+    for loc in locations:
         if loc is not None:
+            logging.info("Searching for config file in '%s'", loc)
             config_path = loc + '/PDMameUpdate.json'
             if pathlib.Path(config_path).is_file():
                 config_file_loc = config_path
                 break
 
+    if 'config_file_loc' not in locals():
+        logging.error("Config file not found")
+        raise FileNotFoundError("Config file not found")
+
     logging.info('Opening config file: '+config_file_loc)
-    config_file = None;
+    config_file = None
     with open(config_file_loc, 'r') as config_file:
         config = json.load(config_file)
+        parameters = [
+            "mame-directory",
+            "pleasuredome-password",
+            "pleasuredome-user",
+            "torrent-directory",
+            "transmission-password",
+            "transmission-port",
+            "transmission-user"
+        ]
+        for key in parameters:
+            if key not in config:
+                logging.error('Missing key in config file: %s', key)
+                raise ValueError('Invalid config file.')
         return config
 
 
@@ -251,6 +275,7 @@ def update_torrents():
             t = requests.get(torrent['remote-link'], verify=False)
             open(new_torrent, 'wb').write(t.content)
 
+
 if __name__ == '__main__':
     logging.basicConfig(
         level=logging.WARNING,