Update mystery yaml parser to a maintained package module

Tested on both local files and url-files and works great.

Mystery.py

@@ -4,33 +4,12 @@ import random
 import urllib.request
 import urllib.parse
 import re
+import yaml
 
 from DungeonRandomizer import parse_cli
 from Main import main as DRMain
 from source.classes.BabelFish import BabelFish
 
-def parse_yaml(txt):
-    def strip(s):
-        s = s.strip()
-        return '' if not s else s.strip('"') if s[0] == '"' else s.strip("'") if s[0] == "'" else s
-    ret = {}
-    indents = {len(txt) - len(txt.lstrip(' ')): ret}
-    for line in txt.splitlines():
-        line = re.sub(r'#.*', '', line)
-        if not line:
-            continue
-        name, val = line.split(':', 1)
-        val = strip(val)
-        spaces = len(name) - len(name.lstrip(' '))
-        name = strip(name)
-        if val:
-            indents[spaces][name] = val
-        else:
-            newdict = {}
-            indents[spaces][name] = newdict
-            indents[spaces+2] = newdict
-    return ret
-
 def main():
     parser = argparse.ArgumentParser(add_help=False)
     parser.add_argument('--multi', default=1, type=lambda value: min(max(int(value), 1), 255))
@@ -106,15 +85,11 @@ def main():
 def get_weights(path):
     try:
         if urllib.parse.urlparse(path).scheme:
-            yaml = str(urllib.request.urlopen(path).read(), "utf-8")
-        else:
-            with open(path, 'rb') as f:
-                yaml = str(f.read(), "utf-8")
+            return yaml.load(urllib.request.urlopen(path), Loader=yaml.FullLoader)
+        with open(path, 'r', encoding='utf-8') as f:
+            return yaml.load(f, Loader=yaml.FullLoader)
     except Exception as e:
-        print('Failed to read weights (%s)' % e)
-        return
-
-    return parse_yaml(yaml)
+        raise Exception(f'Failed to read weights file: {e}')
 
 def roll_settings(weights):
     def get_choice(option, root=weights):