Fix multipart error when used via content-type overloading

rest_framework/parsers.py

@@ -122,7 +122,8 @@ class MultiPartParser(BaseParser):
         parser_context = parser_context or {}
         request = parser_context['request']
         encoding = parser_context.get('encoding', settings.DEFAULT_CHARSET)
-        meta = request.META
+        meta = request.META.copy()
+        meta['CONTENT_TYPE'] = media_type
         upload_handlers = request.upload_handlers
 
         try:
@@ -130,7 +131,7 @@ class MultiPartParser(BaseParser):
             data, files = parser.parse()
             return DataAndFiles(data, files)
         except MultiPartParserError as exc:
-            raise ParseError('Multipart form parse error - %s' % six.u(exc.strerror))
+            raise ParseError('Multipart form parse error - %s' % str(exc))
 
 
 class XMLParser(BaseParser):