Force 'utf-8' encoding without relying on platform-dependent default

On Windows, the default encoding is 'cp1252' and this raises a UnicodeDecodeError.

Fix #89 #144 #165

WikiExtractor.py

@@ -2865,10 +2865,23 @@ def process_dump(input_file, template_file, out_file, file_size, file_compress,
     :param process_count: number of extraction processes to spawn.
     """
 
+    def hook_compressed_encoded(encoding):
+        def hook(filename, mode):
+            ext = os.path.splitext(filename)[1]
+            if ext == '.gz':
+                import gzip
+                return gzip.open(filename, mode, encoding=encoding)
+            elif ext == '.bz2':
+                import bz2
+                return bz2.open(filename, mode, encoding=encoding)
+            else:
+                return open(filename, mode, encoding=encoding)
+        return hook
+
     if input_file == '-':
         input = sys.stdin
     else:
-        input = fileinput.FileInput(input_file, openhook=fileinput.hook_compressed)
+        input = fileinput.FileInput(input_file, openhook=hook_compressed_encoded('utf-8'))
 
     # collect siteinfo
     for line in input: