Replace custom set implementation with dictionary from standard library

This gets rid of the deprecated reference to `collections.MutableSet`.

Starting from Python 3.7 the built-in `dict` class is also guaranteed to
preserve order, which can be used after dropping support for Python 3.6.

makehuman/lib/language.py

@@ -43,13 +43,13 @@
 import json
 from getpath import getPath, getSysDataPath, getDataPath
 
-import collections
+from collections import OrderedDict
 
 class Language(object):
     def __init__(self):
         self.language = None
         self.languageStrings = None
-        self.missingStrings = OrderedSet()
+        self.missingStrings = OrderedDict()
         self.rtl = False
 
     def setLanguage(self, lang):
@@ -95,7 +95,7 @@ def getLanguageString(self, string, appendData=None, appendFormat=None):
                 else:
                     result = result + appendData
             return result
-        self.missingStrings.add(string)
+        self.missingStrings[string] = None
         return string
 
     def dumpMissingStrings(self):
@@ -106,78 +106,13 @@ def dumpMissingStrings(self):
         if not os.path.isdir(pathdir):
             os.makedirs(pathdir)
         with open(path, 'w', encoding='utf-8') as f:
-            for string in self.missingStrings:
+            for string in self.missingStrings.keys():
                 if self.language == "master":
                     f.write('"%s": "%s",\n' % (string.replace('\n', '\\n').encode('utf8'), string.replace('\n', '\\n').encode('utf8')))
                 else:
                     f.write('"%s": "",\n' % string.replace('\n', '\\n').encode('utf8'))
 
 
-class OrderedSet(collections.MutableSet):
-    """
-    Set that maintains insertion order.
-
-    This is a python recipe, as referenced in the official documentation
-    (http://docs.python.org/2/library/collections.html)
-    Source: http://code.activestate.com/recipes/576694/
-    """
-
-    def __init__(self, iterable=None):
-        self.end = end = [] 
-        end += [None, end, end]         # sentinel node for doubly linked list
-        self.map = {}                   # key --> [key, prev, next]
-        if iterable is not None:
-            self |= iterable
-
-    def __len__(self):
-        return len(self.map)
-
-    def __contains__(self, key):
-        return key in self.map
-
-    def add(self, key):
-        if key not in self.map:
-            end = self.end
-            curr = end[1]
-            curr[2] = end[1] = self.map[key] = [key, curr, end]
-
-    def discard(self, key):
-        if key in self.map:        
-            key, prev, next = self.map.pop(key)
-            prev[2] = next
-            next[1] = prev
-
-    def __iter__(self):
-        end = self.end
-        curr = end[2]
-        while curr is not end:
-            yield curr[0]
-            curr = curr[2]
-
-    def __reversed__(self):
-        end = self.end
-        curr = end[1]
-        while curr is not end:
-            yield curr[0]
-            curr = curr[1]
-
-    def pop(self, last=True):
-        if not self:
-            raise KeyError('set is empty')
-        key = self.end[1][0] if last else self.end[2][0]
-        self.discard(key)
-        return key
-
-    def __repr__(self):
-        if not self:
-            return '%s()' % (self.__class__.__name__,)
-        return '%s(%r)' % (self.__class__.__name__, list(self))
-
-    def __eq__(self, other):
-        if isinstance(other, OrderedSet):
-            return len(self) == len(other) and list(self) == list(other)
-        return set(self) == set(other)
-
 def getLanguages():
     """
     The languages available on this MH installation, by listing all .json