Changed the mimetype detection code to only read first 4k block of file, not the whole file.

 - Legacy-Id: 5878

Author: levkowetz

ietf/submit/parsers/plain_parser.py

@@ -32,7 +32,7 @@ def parse_max_size(self):
     def parse_file_charset(self):
         import magic
         self.fd.file.seek(0)
-        content = self.fd.file.read()
+        content = self.fd.file.read(4096)
         if hasattr(magic, "open"):
             m = magic.open(magic.MAGIC_MIME)
             m.load()