Remove stray pychecker directive.

Lib/email/mime/nonmultipart.py

@@ -14,13 +14,9 @@ from email.mime.base import MIMEBase
 class MIMENonMultipart(MIMEBase):
     """Base class for MIME multipart/* type messages."""
 
-    __pychecker__ = 'unusednames=payload'
-
     def attach(self, payload):
         # The public API prohibits attaching multiple subparts to MIMEBase
         # derived subtypes since none of them are, by definition, of content
         # type multipart/*
         raise errors.MultipartConversionError(
             'Cannot attach additional subparts to non-multipart/*')
-
-    del __pychecker__