demandimport: blacklist rfc822 and mimetools to prevent spurious warnings

mercurial/demandimport.py

@@ -137,6 +137,8 b' ignore = ['
     # raise ImportError if x not defined
     '__main__',
     '_ssl', # conditional imports in the stdlib, issue1964
+    'rfc822',
+    'mimetools',
     ]
 
 def enable():